He has deserved the cushion; a saying of one whose wife is brought to bed of a boy: implying, that having done his business effectually, he may now indulge or repose himself.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
Curtezan * Cushion ThumperNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes