Green’s Dictionary of Slang

windward passage n.

the anus.

1726		Weekly Journal, or The British Gazetteer 1 Oct. n.p.: Monday one Thomas Doulton stood upon the pillory at Charing-Cross, pursuant to his sentence at the last Sessions at the Old Bailey, for endeavouring (according to the canting term) to discover the Windward Passage upon one Joseph Yates, a seafaring person.
1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue n.p.: Windward passage, one who uses, or navigates the windward passage; a sodomite.
1811		Lex. Balatronicum.
1999		Roger’s Profanisaurus 3 in Viz 98 Oct. 5: bottom log n. A scuttled dreadnought (qv) that hits the sea bed whilst still exiting the windward passage.

In phrases

navigate the windward passage (v.)

to sodomize.

1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue n.p.: Windward passage, one who uses, or navigates the windward passage; a sodomite.
1999		Guardian Sport 9 Apr. 16: He prefers to navigate the windward passage. He likes to lead his lama up the marmite motorway.

navigator of the windward passage (n.)

a sodomite, a male homosexual.

1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue.
1811		Lex. Balatronicum.
1997		Roger’s Profanisaurus in Viz 87 Dec. n.p.: navigator of the windward passage euph. Rear admiral (qv).