Jock. "Jock" is slang for "athlete." It was originally short for "jockey," someone who rides racehorses.
Perhaps I should mention that male athletes usually wear something, politely known as an "athletic supporter," commonly known as a "jockstrap," to hold their testicles close to their body. "Jock" is not a bad word, but it does have associations with "jockstraps" and "locker-room talk" (vulgar talk in an all-male environment).
"Nerd" is interesting; the word emerged in my lifetime, around the 1970s. The best guess as to its origin is that it was invented by a writer, "Dr. Seuss," in a 1950s children's book called "If I Ran the Zoo." Dr. Seuss liked to invent fabulous imaginary animals, and invent names for them, and the narrator imagines bringing back strange creatures from all over the world:
"I'll bring back an It-kutch, a Preep and a Proo,
A Nerkle, a Nerd, and a Seersucker, too!"
That's thought to be the first appearance in print, but how it acquired its present meaning is unknown.