Green’s Dictionary of Slang

dorse v.¹

to sleep (with).

1789		implied in dorse upon the queer roost
1812		Vaux Vocab. of the Flash Lang. in McLachlan (1964) 236: To dorse with a woman, signifies to sleep with her.
1823		Egan Grose’s Classical Dict. of the Vulgar Tongue.
1846		Punch XI, 165: Then silent flowed the tears of those maidens as perforce, Each saw her favourite champion sent, as Bell’s Life says, dorse [F&H].
1852		Kendal Mercury 3 Apr. 6/1: ‘Well, Dick,’ enquires the donna, ‘did ye see many coves what are likely to dorse (sleep) here this darkey?’.
1897		J. London ‘The Road’ in Hendricks & Shepherd Jack London Reports (1970) 311–21: dorse or kip, to sleep.

In phrases

dorse upon the queer roost (v.) [queer adj. (1); the arrangement is ‘queer’ because it is fraudulent]

to live together as man and wife.

1789		G. Parker Life’s Painter 140: We dors’d some time together upon the queer-roost, but now we come to the rum-snooze at once.
1801		G. Hangar Life, Adventures and Opinions II 60: Your flash-man, [...] is dorsing a darkey upon the queer roost with some other rum blowen.
1833		‘The Christening of Little Joey’ in Corinthian in Spedding & Watt (eds) Bawdy Songbooks (2011) IV 45: [as 1789].