Green’s Dictionary of Slang

1. a sheep.

1984

Partridge DSUE (8th edn) 92/1: C.128-mid–19C.

2. a calf.

1703		Hell Upon Earth 5: Blater, a Calf.
1708		J. Hall Memoirs (1714) 11: Blater, a Calf.
c.1786		Grose Classical Dict. of the Vulgar Tongue ms. additions n.p.: Blater a Calf. Cant.
1788, 1796		Grose Classical Dict. of the Vulgar Tongue (2nd, 3rd edn).
1811		Lex. Balatronicum.
1828		Lytton Pelham III 295: ‘What ho, my kiddy,’ cried Job, ‘don’t be glimflashy. Why you’d cry beef on a blater.’.