Green’s Dictionary of Slang

of a woman, pregnant.

1889–90		Barrère & Leland Dict. of Sl., Jargon and Cant.
1890–1904		Farmer & Henley Sl. and Its Analogues.
c.1900		‘Ramrod’ Nocturnal Meeting 143: Boys, if you get Mrs Aintree’s belly up [...] I’l give you a bicycle apiece.
1937–84		Partridge DSUE (1984) 68/2: C.17–early 20.