Green’s Dictionary of Slang

jock n.1

also jocum, jok-e
[jockum n.]

1. [mid-18C+] the genitals, both male and female; also in fig. use [the word vanished from the mainstream but remains in US black in the late 20C+].

2. as a garment.

(a) [1920s+] an athletic support or ‘jock strap’.

(b) [1950s+] (Aus./Irish/US, also jockettes) in pl., underwear, usu. men’s.

3. [1940s+] (US campus and sporting, also jocko, jockette, jockstrap) a sportsman, esp. an assiduously keen one; also attrib.

4. [1960s+] (US campus) a politically conservative, white, middle-class young man.

5. [1960s+] (US campus) as ext. of sense 3, a devoted and diligent student, e.g. math jock, computer jock.

6. [1980s+] (US) a stupid, unimaginative person, a nerd.

7. see jocker n.1 (3)

In derivatives

jocky (adj.)

sporty, ostentatiously ‘masculine’.

In compounds

jock major (n.)

[1960s+] (US campus) a student who majors in physical education.

jock-piece (n.)

[1920s+] (US) the penis.

jock-rot (n.) (also jock itch, jock rash)

[1960s+] (US) a fungal infection of the genital area, common amongst atghletes and stimulated by steam rooms, e.g. gymns, laundries.

jocksniffer (n.) [joc. use of sense 1 above + SE sniffer; note reported 2003 US Army use, a civilian who is very wrapped up in military affairs]

[1960s+] (US) a (presumably male) sports groupie who likes to hang around sports stars.

jockstrap (n.)

1. [1960s+] (US) a stupid, insignificant fellow.

2. see sense 3 above.

In phrases

black jock (n.)

1. [mid–19C] the pubic hair.

2. [late 19C] (also brown jock, grey jock) the vagina.

go jock-hunting (v.)

[late 19C–late 1900s] to have sexual intercourse.

knock someone’s jock off (v.) (also beat someone’s jock off)

[1950s+] (US) to overcome completely.

lose one’s jock (v.)

[1960s+] (US) to be fooled.

on someone’s jock(strap)

[1980s+] (US) pursuing, esp. of a woman sexually harassing a man.