conundrum, n. — Green’s Dictionary of Slang

conundrum n.

[SE conundrum, ‘a whim, crotchet, maggot, conceit’; ? intensified by 19C ‘a thing that one is puzzled to name, a “what-d’ye-call-it”’ (OED)]

the vagina.

1652		R.W. Pill to Purge Melancholy in Marshburn & Velie Blood and Knavery 1159: The lawyer began afresh to court his mistress, and to kiss and hug her close to him, proffering to feel her conundrum.
1890–1904		Farmer & Henley Sl. and Its Analogues.
1896		Farmer Vocabula Amatoria (1966) 101: Écoutille (l’), f. The female pudendum; ‘the conundrum’.
1972		J.B. Keane Letters of Irish Parish Priest 5: ‘Oh Lord Jaysus,’ she said. ‘That’s the size of an orange. ’Tis as big as an elephant’s conundrum.’.