Green’s Dictionary of Slang

the vagina.

1890–1904		Farmer & Henley Sl. and Its Analogues.
1896		Farmer Vocabula Amatoria (1966) 195: Noc, m. The female pudendum; ‘the tenuc.’ [An anagram = con].
1909		G.R. Bacchus Maudie 62: The one mystic word ‘Tenuc,’ which, as all our readers possibly know, is back slang for cunt.
1980		Maledicta IV:2 (Winter) 183: Then there are the euphemisms used in more respectable literature [...] what were presumably originally pet names such as her fan (short for fanny probably the commonest semi-polite term for the tenuc [backslang] in the U.K. In the U.S.A. this word more commonly refers to the posteriors).
1992		R.G. Barrett Davo’s Little Something 13: Righto-teenuck-head.