Green’s Dictionary of Slang

1. (also gotcher! got ya!) I understand! OK!

1920		T. Thursday ‘Mr. Mister’ in All-Story Weekly 22 May 🌐 ‘Get me?’ ‘Gotcher!’ says Purcell.
1954		C. Chessman Cell 2455 66: ‘I’ll meet you here tonight around six.’ ‘Got ya,’ Tim said.
1969		N. Spinrad Bug Jack Barron 32: ‘Ah,’ he said. ‘Gotcha!’.
1978		F. Norman Dead Butler Caper 38: Okay – five minutes – gotcha!
1983		C. Heath A-Team 2 (1984) 125: ‘Nobody comes through that door but me.’ ‘Gotcha, boss,’ Harmson replied.
2000		Guardian G2 17 May 9: ‘It looks as if she’s been re-filed under her mother’s name.’ Gotcha!

2. (also gotcher!) I have got you! [the locus classicus was the 1981 Sun newspaper headline Gotcha! on the drowning of the crew of the Argentine warship Belgrano].

1932		E. Wallace When Gangs came to London (2001) 144: The ’plane was nearing the centre of Cavendish Square, when it suddenly heeled over [...] and it fell with a crash in the centre of the garden which occupied the middle of the square. ‘Gotcher!’ It was Jiggs’ triumphant voice .
1952		J. Jones From Here to Eternity (1998) 542: Boom! Boom! Gotcha, gotcha! You’re dead! Boom!
1964		P. Terson Night to Make the Angels Weep (1967) II xvi: Gotcher then.
1974		(con. 1940s) E. Thompson Tattoo (1977) 53: ‘Race you to the end of the bridge.’ He was off like a shot. ‘Gotchercockout!’ he cried.
1981		Sun (London) 4 May [headline] Gotcha! Our lads sink gunboat and hole cruiser.
1999		K. Sampson Powder 128: He groped for his jeans and worked his fingers into the tiny hip pocket. Aha! Gotcha, you boundah!

3. attrib. use of sense 2 .

2006

C.W. Ford Deuce’s Wild 52: I turned back toward the bouncer. He had a ‘gotcha’ smile on his face.