Why Are Harley-Davidson Motorcycles called Hogs
It is believed that the term "hog," in referring to a Harley-Davidson® motorcycle, traces back to the early 1920s. The official Harley-Davidson company racing team of that era was known as the "Wrecking Crew" because of their nearly total domination of the dirt track races they entered.
An additional member of the team (a mascot not a racer) was a small pig. Whenever a Wrecking Crew team member won a race, he stopped to pick up the pig, put on the gas tank, and took it with him for a victory lap. After a while, race fans and some in the media began to informally refer to the team as the "Harley Hogs." Over time, the "Wrecking Crew" moniker stuck and people stopped referring to the team as the “Harley Hogs”.
However, as the "Harley Hogs" nickname faded, the word "hog" stuck as the slang term among enthusiasts for a Harley-Davidson motorcycle. The 3rd Edition of the Dictionary of American Slang even contains an entry for "hog" as being a "1960s motorcycle or motorcyclist" with a following entry mentioning Harley-Davidson by name. The word then became more official in 1983 when the world's first factory-sponsored motorcycle club appeared. The choice must have been obvious: The Harley Owners Group®, or HOG®.