Green’s Dictionary of Slang

a venereal bubo.

a.1664		J. Denham Pooley and Killigrew 105: Whether it Pullen be or Shanker, / Corded and crooked like an Anchor, / Your cure too costs you but a Spanker.
c.1698		B.E. Dict. Canting Crew n.p.: Poulain a Bubo.
1725		New Canting Dict. [as cit. c.1698].
1737, 1759, 1760, 1776		Bailey Universal Etym. Eng. Dict. [as cit. c.1698].
1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue.
1811		Lex. Balatronicum.