gertcha!, excl. — Green’s Dictionary of Slang

gertcha! excl.

also gerch you! gertch! gertcher!

[lit. or fig. get away with you!/get along with you! excl.]

a mocking response, either aggressive or affectionate.

1935		in A. Livingstone et al. Peace Ballot 22: Gertcha! We ain’t all fools in Birmingham, if you think we are!
1938		X. Herbert Capricornia (1939) 234: Gertch — you old blowbag! You’re only humming for a drink. Nick off home.
1947		J. Maclaren-Ross Of Love And Hunger 9: ‘Come Christmas we’ll all be in it.’ ‘Gertcher.’.
1958		(con. 1940s) B. Behan Borstal Boy 214: ‘Gerch you,’ said Charlie.
1980		Barltrop & Wolveridge Muvver Tongue 97: ‘Gertcher’ or ‘gertcha’ [...] has received a new lease of life from a popular song.