From Vetstreet's Dr. Marty Becker:

While most of the country has had a hot streak or two this summer, those weren’t officially “dog days” unless they occurred in late July or August — at least in the Northern Hemisphere.

That’s because the term “dog days” refers to a period when Sirius — the “dog star,” part of the constellation Canis Major — is brightest in the summer sky. The ancient Romans marked these days from July 23-24 to August 23-24, noting that they were typically the hottest days of the year. Eventually, the phrase “dog days” came to mean any hot streak in the summer.

Did you know that? The reason I did is because I love learning new things. I always have, and I hope I always will. I’ve always clipped interesting stories from newspapers and magazines, and in a way I still do, although these days I usually snap a picture with my smartphone and send it to friends and family.

I’ve gone through my files — and two of my own books — to find five tidbits worthy of being part of a Trivial Pursuit edition just for dog lovers. (And, yes, I’ll put together one for cat lovers, too!) Hope you enjoy these!

Five Surprising Things You Didn't Know About Dogs

The origin of dog tags: Putting collars on dogs is an ancient practice, but dog licenses are much more recent. In the United States, at least, the practice is a little more than a century old, and it started in Cincinnati, Ohio. Charging dog owners to license their pets caught on with other cities as well and was so common that by the time American soldiers in World War I were issued ID tags, they reminded everyone so much of what dogs wore that they were humorously called “dog tags,” a term that sticks to this very day.

Guard dog on duty: The phrase "Beware of Dog" is so old that its Latin equivalent — "cave canem" — has been found on signs in Roman ruins. The word "watchdog" isn't quite so old; the first mention of it is by Shakespeare, in The Tempest.

First-aid cream is better: The idea that a dog's saliva has healing powers has been around at least since the ancient Greeks and Romans, whose physicians believed it to be an antidote for poisoning. Later, St. Roch was often pictured with a dog licking a sore, reflecting the belief that the patron saint of plague victims knew something about a cure and that his dog's saliva made him healthy. Modern medicine, no surprise, doesn't look kindly on such theories. And by the way: Dogs are attracted to open wounds because the serum from them is sweet.

Doggie dreads: If you let the hair of Poodles grow, it will form dreadlocks. While not common, Poodles with “cords” do turn up at dog shows now and then, and they always attract attention. While pet Poodles are typically kept in a short “puppy clip” and show Poodles are groomed for fluffy, big hair, there are breeds who cannot be shown competitively without their cords: the Puli and the Komondor. In Europe, the Bergamasco is shown not only corded but also matted, with what look like large pieces of felt hanging from his pelt. Cords are impractical for pet dogs, which is why these breeds are often shorn of their distinctive coats when they’re retired from showing. A few years back, a top-winning American Komondor was shaved down, losing 2,700 cords and 15 pounds in the process.

Fleas aren’t picky: When dogs have fleas, it’s more likely they’ll be what are called “cat fleas,” or Ctenocephalides felis. As for cats, they’re more likely to have cat fleas, too. There is a “dog flea,” but it’s nowhere near as common. The reason “cat fleas” are named after our feline companions is pure coincidence: They were found on a cat when they were first named, in 1834. And, yes, modern flea control from your veterinarian will control these heinous hitchhikers on both cats and dogs.

These are just the tip of the iceberg. I’ll share more bits of canine trivia another time. Hope you enjoyed these!

More on Vetstreet:
14 Common Dog Behavior Myths Decoded
15 Worst Dog Breeds for New Pet Owners
Why Does My Dog Twitch While Sleeping?
Save Your Dog’s Life in 5 Easy Steps
367 Dogs Rescued From Alleged Fighting Ring

Also on HuffPost:

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  • NEW YORK, NY - JANUARY 30: Gibbs, a Golden Retriever puppy poses for pictures as the American Kennel Club Announces Most Popular Dogs in the U.S. on January 30, 2013 in New York City. (Photo by Gary Gershoff/Getty Images for the American Kennel Club)

  • A view of a puppy at the North Shore Animal League America's Tour For Life Pet Adoption Event on April 26, 2012 in New York, United States. (Photo by Cindy Ord/Getty Images)

  • A Samoyed puppy waits with its owner in a park as Beijing enjoys a pollution free spring day on April 18, 2013. The breed which is originally from Siberia were used to herd reindeer and pull sleds and were able to survive the harsh winters with their thick coats. AFP PHOTO/Mark RALSTON

  • Two Beagle puppies play as the American Kennel Club officials announce their annual list of the most popular dog breeds in the U.S January 27, 2010 in New York. (DON EMMERT/AFP/Getty Images)

  • Puppies watch on at a police dog training base September 16, 2005 in Beijing, China. The dogs are trained by a police squad to learn identifying, catching, tracking and other skills. According to the Ministry of Public Security, there is an estimate of over 10,000 working police dogs in China. These dogs are divided into 30 kinds according to international conventions and are widely used in police work, rescue and military missions. (Photo by China Photos/Getty Images)

  • A view of a puppy at the North Shore Animal League America's Tour For Life Pet Adoption Event on April 26, 2012 in New York, United States. (Photo by Cindy Ord/Getty Images)

  • A view of a puppy at the North Shore Animal League America's Tour For Life Pet Adoption Event on April 26, 2012 in New York, United States. (Photo by Cindy Ord/Getty Images)

  • NEW YORK, NY - JANUARY 30: Dominique, a Bulldog puppy poses for pictures as the American Kennel Club Announces Most Popular Dogs in the U.S. on January 30, 2013 in New York City. (Photo by Gary Gershoff/Getty Images for the American Kennel Club)

  • A wolf plays with a one-month-old puppy in its enclosure of Berlin's Zoo on May 31, 2013 in Berlin. AFP PHOTO / JOHANNES EISELE

  • Puppies just born by a sniffer dog sleep at a police dog training base September 16, 2005 in Beijing, China. The dogs are trained by a police squad to learn identifying, catching, tracking and other skills. According to the Ministry of Public Security, there is an estimate of over 10,000 working police dogs in China. These dogs are divided into 30 kinds according to international conventions and are widely used in police work, rescue and military missions. (Photo by China Photos/Getty Images)

  • A Mastiff puppy rests during the XVIIIth International Dog exhibition on November 8, 2009 in Prague. (MICHAL CIZEK/AFP/Getty Images)

  • A three-day-old Labradoodle puppy is shown to the press at the Uri Bekman's 'World of Dogs' kennel in Pardesia, 30 kms north of Tel Aviv 07 December 2005. (YOAV LEMMER/AFP/Getty Images)

  • Three-day-old Labradoodle puppies nap at the Uri Bekman's 'World of Dogs' kennel in Pardesia, 30 kms north of Tel Aviv 07 December 2005. (YOAV LEMMER/AFP/Getty Images)

  • A seven week old Daschund cross puppy waits to be re-homed at the Cheshire Dogs Home on January 4, 2010 in Warrington, England. (Photo by Christopher Furlong/Getty Images)

  • Three-year-old Galia suckles her first litter of six puppies on June 4, 2009 at the Barry Foundation Great St. Bernard breeding kennels in Martigny, Western Switzerland. (FABRICE COFFRINI/AFP/Getty Images)

  • Two-week-old puppies play on June 4, 2009 at the Barry Foundation Great St. Bernard breeding kennels in Martigny, Western Switzerland. (FABRICE COFFRINI/AFP/Getty Images)

  • Two-week-old Saint Bernard puppies play at the Barry Foundation breeding kennels in Martigny on June 4, 2009. The Saint Bernard dog was once the ubiquitous companion of monks at the monastery tucked 2,500m above sea level, guiding them through the Alps or helping them to rescue stranded or lost travellers in the snowy mountains. However, there are no longer any such dogs living permanently at the monastery these days. In fact, the monks decided five years ago to part ways with their pedigree breeding programme, as the work became too much for the four monks living permanently at the monastery to handle. The breeding kennels faced the risk of being shut permanently if not for a group of Swiss bankers and animal-lovers who set up the Barry Foundation to buy the breeding programme. (FABRICE COFFRINI/AFP/Getty Images)

  • Two puppies play as American Kennel Club officials announce their annual list of the most popular dog breeds in the U.S January 27, 2010 in New York. (DON EMMERT/AFP/Getty Images)

  • A volunteer holds up a puppy that was born after its mother has been rescued from a truck, in an animal hospital in Beijing, China, Tuesday, April 19, 2011. Chinese animal lovers mobilized by online calls for help blockaded a truck of hundreds of dogs being shipped off for food in a rare, permitted display of social action amid a broad crackdown on most kinds of activism. (AP Photo)

  • Nine Rhodesian Ridgeback puppies from a litter of 17 look out of their box in Nauen, 50 kilometers outside Berlin on Monday, Dec. 20, 2010. On Sept 28, and 29, 4 year old Ridgeback Etana had 17 puppies. All of them survived. (AP Photo/Markus Schreiber)

  • Seven Rhodesian Ridgeback puppies from a litter of 17 look out of their box in Nauen, 50 kilometers outside Berlin on Monday, Dec. 20, 2010. On Sept 28, and 29, the 4 years old Ridgeback Etana had 17 puppies. All of them survived. (AP Photo/Markus Schreiber)

  • A puppy is transported in a child's push chair, on a snowy street downtown Bucharest, Romania, Friday, Dec. 17, 2010. (AP Photo/Vadim Ghirda)

  • A seven week old Border Collie puppy rests after frolicking with its sibblings in their garden as outdoors temperatures dropped below minus 10 degrees celsius in the village of Bodice on December 16, 2010. (JOE KLAMAR/AFP/Getty Images)

  • A seven-week old Border Collie puppy rests after a play with its siblings in their garden as outdoors temperatures dropped below minus 10 degrees celsius in the village of Bodice on December 16, 2010. (JOE KLAMAR/AFP/Getty Images)

  • Six-month old Chihuahua puppies, Ellie, left, and Gulliver, right, nuzzle together at the Massachusetts Society for the Prevention of Cruelty to Animals, in Methuen, Mass. Wednesday, June 15, 2011. The already adopted puppies, born without front legs, were fitted with wheels made by Eddie's Wheels of Shelburne, Mass. and are training to walk and run with them. (AP Photo/Elise Amendola)

  • Puppies run at a playground in the K9 school and hospital of the Middle East Kennel Cub at Nahr al-Kalb area, north of Beirut, on October 27, 2010. The Club, which is the largest in the Middle East, has more than 400 dogs and clients bring their pets to be trained, bred and hospitalized. (JOSEPH EID/AFP/Getty Images)

  • In this handout image provided by Pucchin Dog's, 'Love-Kun', a 3-day old chihuahua puppy with heart-shaped markings is presented to the media with his brothers at Pucchin Dog's on August 6, 2009 in Odate, Akita prefecture, Japan. The new puppy is the brother of 2-year old chihuahua 'Heart-Kun' who was also born with a perfect heart-shaped marking on his back from the same parents. (Photo by Pucchin Dog's via Getty Images)

  • This photo provided by the Chicago Zoological Society shows 10 African wild dog puppies, six males and four females, huddling with their mother, Kim, at Brookfield Zoo in Broofield, Ill. (AP Photo/Chicago Zoological Society, Jim Schulz)

  • In this Thursday, May 19, 2011, photo, Bonnie, a basset hound, nurses her puppies at an animal rescue facility in South Knox County, Tenn. Bonnie and Clyde, the father of her puppies, are being cared for by At Risk Intervention animal rescue, after being saved from flood waters in Arkansas. (AP Photo/The Knoxville News Sentinel, Paul Efird)

  • Two adopted stray dogs play at an animal shelter on December 15, 2006 in the outskirts of Xian of Shaanxi Province, China. The animal shelter, established by Chinese animal lover Dai Shuqing, is located at an abandoned warehouse which houses some 100 dogs and costs over 2,000 yuan (about US $255) per month. (Photo by China Photos/Getty Images)

  • Golden Retriever puppies with their handlers as the American Kennel Club officials announce their annual list of the most popular dog breeds in the U.S January 27, 2010 in New York. (DON EMMERT/AFP/Getty Images)

  • Susan Thomson holds a three-week-old Chihuahua puppy named Tom Thumb on April 7, 2009 in Renton, Scotland. An unofficial measurement taken by the owner makes Tom Thumb approximately 6 inches long. (Photo by Jeff J Mitchell/Getty Images)

  • A dog suckles her puppies on February 16, 2009 at Halikisla village of Kars, eastern Turkey near the border with Armenia. (MUSTAFA OZER/AFP/Getty Images)

  • A six month old Weimaraner puppy guards his master during Slovakia's national canine all breeds competition in Banska Bystrica on 6 May 2007. (JOE KLAMAR/AFP/Getty Images)

  • Portuguese Podengo puppies are displayed for the media during the launch of the Crufts Dog Show Febuary 24, 2004 in London, England. (Photo by Scott Barbour/Getty Images)