Green’s Dictionary of Slang

Naples canker n.

syphilis.

1598		Marston Metamorphosis of Pigmalions Satyre 2 48: Which I am sure is all thou brought’st from France, Saue Naples poxe.
1598		Marston ‘Fronti nulla sides’ Satyres I B6: To his owne sprouts, marke, his rank drops distill / Foule Naples canker in their tender rinde.
1620		J. Taylor ‘Praise of Hemp-Seed’ in Works (1869) III 65: There’s many a Gallant dallying with a Drab, / Hath got the Spanish pip, or Naples scab, / The Galliae Morbus or the Scottish fleas, / Or English Poxe, for all’s but one disease.
1621		J. Howell Familiar Letters (1737) I 21 Aug. 67: The young Maid having understood that Don Baltran had been in Naples, and had that Disease.
a.1661		‘The Four-legg’d Quaker’ Rump Poems and Songs (1662 ) I 361: Alas you know by Man’s flesh came / The Foul-disease to Naples.
1734		C. Johnson Hist. of Highwaymen &c. 101: She very civilly tipped me a Distemper very common in Naples.