Green’s Dictionary of Slang

a Maltese.

1945		D. Bolster Roll On My Twelve 20: I got bit by a bloody Malt in a bit of a lark.
1959		C. MacInnes Absolute Beginners 40: The two beefo Malts who walked between us, oozing virility and no deodorant.
1962		R. Cook Crust on its Uppers 58: Malts, spades, bubbles and the queans that beat ’er black an’ blue.
2006		in D. Seabrook Jack of Jumps (2007) 50: One of the Malts was badly burned.