Don Cypriano, n. — Green’s Dictionary of Slang

Don Cypriano n.

[play on Sp. honorific Don + Cyprian adj.; coined by Sir Thomas Urquhart for his translation of Rabelais (1653–93)]

the penis.

1653		Urquhart (trans.) Gargantua and Pantagruel (1927) I Bk II 335: [He] showed his bel vedere to the world, together with his Don Cypriano, which was no small one.
1890–1904		Farmer & Henley Sl. and Its Analogues.
1896		Farmer Vocabula Amatoria (1966) 113: Éteuf, m. The penis; ‘Don Cypriano’.