Jerks have been around a very long time. So has the word for
them.
A “jerk” meant the stroke of a whip in the mid 1500s, and
the term for the kind of rapid flick has stayed with us ever since. A Soda Jerk
was so-named due to the fast pulling motion required to work the machine.
An involuntary spasmodic shudder became known as a jerk in
the 1880s, leading to “jerky” movements. To employ such movements deliberately
is to “jerk off,” especially if you are a man.
To be a jerk — a tedious person — comes from the implication
that you are the kind of guy who masturbates a lot. One presumes the idea is
that such a person is self-obsessed to the point of social ignorance. (In Great
Britain, there is a direct correlation with the words “wank,” and “wanker,”
although the insult is far greater.)
Jerky, on the other hand, also refers to thin slices of
dried, often seasoned, preserved red meat. The word comes from the Quechua
(Incan) word “charqui,” dried flesh.
A “jock” is an athletic man, from “jockstrap,” a protective
supporter for the genitals often worn by athletes. Although jocks have long
existed, the terminology is surprisingly recent — dating from the 1950s.
Jokes have been played for as long as people have had a
sense of humor, which might go all the way back to the time when proto-humans
were puddles of slime wobbling with laughter. The Romans called a joke a
“iocus,” which became, via the French in the 1660s, a “joque,” a jest.
It is possible, then, for a jock who is a jerk to be jerkily
jerking jocularly off while wearing a jockstrap, thinking about being jerked
and eating jerky, as a joke.