Green’s Dictionary of Slang

pain in the arse n.

also ass-pain, pain in the ass, ...asshole, ...backside, ...balls, ...bleep, ...bum, ...butt, ...bustle, ...can, ...clinkers, ...fanny, ...hole, ...kazakis, ...whoosis, boil in the arse, p.i.t.a.
[arse n. (1)/ass n. (2)/asshole n. (1)/backside n. (1)/balls n. (1)/bleep n./bum n.1 (1)/butt n.1 (1a)/clinkers n. (4)/hole n.1 (1a)/whoozis n. (2)]
[1930s+]

1. a feeling of irritation; usu. as give someone a pain in the arse

2. an annoying person.

3. an annoying object, situation or circumstance.

In phrases

give someone a pain in the arse (v.) (also give someone a pain in the ass, ...behind, ...bum, ...can, ...foot, ...pants, ...tail, ...an ache in the back of their lap) [ass n. (2)/bum n.1 (1)/can n.1 (1b)/tail n. (1)]

[20C+] of people, objects or situations, to irritate someone.