The "jocks" of today are all about sports, but in its beginnings, "jock" (like "jack" in English) was simply Scottish for "guy."
"Jock" was a catchall phrase for men performing any number of odd jobs (hence the expression "jack of all trades"). With time and the industrial revolution, "jock" became short for "jockey" and came to mean anyone who operated machinery or rode a horse.
In 1874, the Bike Athletic Company of Tennessee decided to create an undergarment "suspensory" for the men who were being jarred while "jockeying" through the cobblestone streets of Boston on bicycles. The suspensory quickly came to be known by a more common slang name: the jock strap. Men started using it for support during all types of athletic activity, not simply bike riding.
During the early epoch of male college sports in the 1920s and '30s, "jocks" were the people who most vigorously supported athletics--especially the sporty university boys concerned with the masculinity that making the team might confer.
The word was used in a tongue-in-cheek way--people have always poked fun at anyone so concerned with being macho--but being a jock wasn't so bad. Jocks were generally considered genial and, at least in mainstream media, always "got the girl."
That started changing with the counterculture wars of the 1960s and '70s, when sports such as football came to represent all that was militaristic, imperialistic and rapacious in our society. After the Columbine school shooting in 1999, when Dylan Klebold and Eric Harris attributed some of their murderous rage to the torment they'd reported receiving at the hands of school athletes, anti-jock sentiment finally seemed to hit the mainstream.
Today, jock has lost its hazy innocence. While it is still used to describe someone who is simply into sports, the jock we've come to love to hate is overly obsessed with them, tends to malign artistic and intellectual endeavors and may on occasion like to use brute strength to bully others.
