Green’s Dictionary of Slang

(gay) to allow anal intercourse.

1938–52		in G. Legman Limerick (1953) 57: There was a young girl of Cape Cod / Who dreamt she’d been buggered by God. / But it wasn’t Jehovah / That turned the girl over, / ’Twas Roger the lodger, the dirty old codger, / The bugger, the bastard, the sod!
1941		in E. Cray Erotic Muse (1992) 106: I loved so sweet and I kissed so neat / Till I got her to turn over.
1965		Guild Dict. Homosexual Terms 46: turn over (v.): To allow oneself to be pedicated.