Green’s Dictionary of Slang

the buttocks.

1611		R. Cotgrave Dict. of Fr. and Eng. Tongues n.p.: Cul [...] An arse, bumme, tayle, nockandroe, fundament.
1653		Urquhart (trans.) Gargantua and Pantagruel (1927) I Bk I 51: My foul nockandrow, all bemerded / In shitting.
1654		E. Gayton Pleasant Notes I iv 14: Blest be Dulcinea, whose Favour I beseeching, / Rescu’d poore Andrew, and his Nock-Andro from breeching.