Green’s Dictionary of Slang

oven n.

1. [early 16C–19C; 1980s] the vagina.

2. [late 18C–mid-19C] a large mouth.

3. [1950s+] the womb; usu. in phrs. below.

In phrases

have a bun in the oven (v.) (also have a bun in the club, …in one’s tin, …a scone in the oven, have bread in the oven, in the oven) [mid-19C; 1950s+]

1. to be pregnant.

2. of a man, to impregnate one’s partner.