這個拼法底下其實是2個不同的字，意思沒有關係， 只是長得一樣。下面分開列出來。跳到 運動咖；體育生 · （英式）蘇格蘭人（常帶冒犯）
One whole side of jock is a long word cut short. The long word here is jockstrap — the piece of kit that sits in a player's bag with the shoes and the towel. Say the kit often enough and it starts to stand for the person wearing it: the jock is the athlete. Around that person a whole school picture gathers — the table where the team sits, the uniform, and the old joke that a big body comes with a small brain. Running alongside is a second short word, jockey, the rider up on top of something, steering it: that one gives the jock who rides the records at a radio station.
The packet's Wiktionary note says the athletic slang meanings date from the mid-20th century and are simple abbreviations of jockstrap, while the computer slang meanings come from jockey.
依證據包裡的 Wiktionary 詞源說明：運動方面的俚語是二十世紀中期出現的，就是 jockstrap 的縮短；而電腦圈的俚語則是從 jockey 來的。所以這一支底下其實有兩條小路，一條從護具，一條從騎師。
Wiktionary entry supplied in the evidence packet (jock, etymology 2 note: 'The computer slang meanings are derived from jockey. The athletic slang meanings in turn date from the mid-20th century and are simple abbreviations of jockstrap.')
From the picture
從一件護具到一個人
這一組就是核心畫面本身：先是裝備，再是穿裝備的人，最後是整個標籤。
noun · B2
In American English, a person — usually a student — who plays a lot of sport and is known for that above everything else. It often carries the old idea that such a person is strong but not clever, so it can be an insult.
運動咖；體育生
駕馭的人
同樣是把長字砍短，但被砍短的是 jockey，不是 jockstrap。
noun · C1
A short, informal word for a disc jockey — the person who plays music and talks between the songs on the radio, or who plays records for a crowd.
（廣播）DJ、節目主持人
noun · C1
A short word for a jockstrap: tight underwear that a man wears under sports clothes to hold and protect the body.
運動護襠（jockstrap 的簡稱）
noun · C1
An informal short word for a jockey — the person who rides a horse in a race.
騎師（口語簡稱）
A second word, same spelling
The other side of jock starts as somebody's name. Jock is the Scottish way of saying Jack, and Jack is a way of saying John — about as ordinary as a man's name gets. English speakers then did what people often do with a very common name: they used it for a type of person instead of for one person. So this jock is a name lifted off one man and laid across a whole country. That is also why it is uncomfortable. A nickname given by a friend sits lightly; the same nickname handed to a stranger because of where he is from usually does not.
From Jock, a Scottish hypocoristic (pet) form of John, compare Jack; the capitalised name is still visible under the common noun.
來自 Jock，也就是 John 在蘇格蘭的暱稱形式，可以跟 Jack 對照。人名的痕跡到今天還看得見——這個意思常常寫成大寫的 Jock。
Wiktionary entry supplied in the evidence packet (jock, etymology 1: 'From Jock, a Scottish hypocoristic form of John (compare Jack)').