Green’s Dictionary of Slang

1. (UK Und.) a slice.

1670		J. Ray Proverbs 188: A shive of my own loaf.
1861		(con. 1840s–50s) H. Mayhew London Labour and London Poor II 227/1: This sort of meat [...] is often eaten in the beer-shops with thick ‘shives’ of bread.
1896		G.F. Northall Warwickshire Word-Bk 209: Shive. A slice.

2. see shiv n.