Green’s Dictionary of Slang

irritability, bad temper.

1860		G.J. Whyte-Melville Market Harborough 104: Old Isaac, [...] subject to occasional ‘rustiness’, and imbued with a strong aversion to what he called being ‘put upon.’.
1900		G.B. Shaw Letter 14 Mar. Coll. Letters: 1898–1910 (1988) 156: In the old days I was always standing between Bland and the rustinesses that used to come from his Tory imperviousness to the Radical notions with which Socialism was adulterated .