the.com/jock

means An athlete, especially a school or college sports star — often used to tag someone by their athletic identity more than anything else about them.

from American slang that grew out of 'jockstrap,' the athletic supporter worn under uniforms, itself from 'jock,' old slang for the male genitals (related to 'jockey'). By the mid-20th century, 'jock' had jumped from the gear to the guy wearing it, becoming campus shorthand for the athletic set — a word that started below the belt and ended up in the yearbook.