Green’s Dictionary of Slang

ballock n.

also bollock
[OE beallucas, itself Teutonic root ball-, thus more immediately ext. of balls n. (1); ballock(s) meant testicle(s) f. 11C but remained SE until late 18C; it appears in Bailey’s Universal Etymological English Dict. in all editions f. 1721–1800 but was not included in Samuel Johnson’s Dictionary, which drew heavily on Bailey’s word-list, in 1755; one must thus assume that the word was passing then from polite use; it was definitely slang by 1800 and appears as such in Grose (1788, 1796) though, oddly, in neither Grose (1785), Hotten nor F&H; thus Ballock Hall, 17C home of Adam & Lucy Loftus, and known for its unsavoury reputation; note single use as a term of affection in Urquhart, The Complete Works of Rabelais (1653): ‘I must gripe thee, my ballock, till thy back crack with it’]

1. [16C+] a testicle; usu. in pl. (for all pl. cits. see ballocks n. (1)).

2. [1940s+] (also bollicky) a general term of abuse.

3. [1970s+] (UK society) a ball (hunt, charity etc) [pun on balls n. (1)].

In compounds

ballock gravy (n.) (also bollock gravy) [gravy n. (1b)]

[2000s] semen.

ballock-hair (n.)

[1990s+] a male pubic hair.

ballock snot (n.) (also bollock snot) [SE snot]

[2000s] semen.

In phrases

drop a ballock (v.) (also drop a bollock)

[1920s+] to make a mistake, to blunder.