Green’s Dictionary of Slang

a tomato.

1920		Chambers’s Jrnl 15 May 384/1: The acreage of ‘outside toms’ is increasing annually .
1973		B.S. Johnson All Bull 29: The cooks [...] doled out tinned toms and greasy bangers.
2001		K. Sampson Outlaws (ms.) 129: Full hit, bacon, sausages, plum tomatoes — got to be plum, can’t have fresh toms with your morning growler, just is not the done thing.