Green’s Dictionary of Slang

1. the vagina.

1672		J. Phillips Maronides (1678) VI 147: In Venus Mount I spie a C / [...] / These C’s these C’s take heed my Son / These C’s has many a man undone.
1819		Beppo in London liv: It was a patent Flute, and not on earth A finer shape’d one ever had been shaken – Besides ’twas perfect in the bottom keys, Which all musicians know are meant for C’s!
1836		‘Come, Sleep With Me’ in Frisky Vocalist 31: And then we’ll plough the deep deep C. [...] The little secret gem of mine, / Around that secret spot of thine.
1838		‘Toasts And Sentiments’ in Rambler’s Flash Songster 48: The three C’s – the rough C – the hairy C – and the open C.
c.1850		The C — , The Open C — [broadside] The C—, the C—. the open C—, / The wide, the deep, and ever free, / Without a pox, without a clap, / It seizes your p—k as caught in a trap, / It drains your c—ds till you call on the gods—, / Then like a gaping gulph it lies.
c.1864		‘Gutta Percha Things’ in Rakish Rhymer (1917) 16: ‘Put out the candle,’ says Miss C., / For I’ve made up my mind to taste your P.’.
1870		Cythera’s Hymnal 14: I’ve sailed into C’s of all sizes, / And in them full often I stick.

2. used as a euph. for swearing.

1936		K. Mackenzie Living Rough 163: Every sentence was well sprinkled with F. C. and B.
2010		(con. 1973) C. Stella Johnny Porno 24: ‘You can be such a cunt’ [...] He knew she hated the C-word.