Green’s Dictionary of Slang

1. a nickname for anyone with red or auburn hair [the colour].

1907		Eve. Star (Wash., DC) 29 Sept. 9/2: I had a glimpse of afreckly face and the silly grin. The party gettin’ the run was Rusty Quinn.
1948		Britannia & Eve (UK) 1 Nov. 28/1: Sub-Lieutenant Rusty Hawkins [...] with his round pudding face and shock of ginger hair.
1959		I. & P. Opie Lore and Lang. of Schoolchildren (1977) 190: Red heads attract a barrage of nicknames: [...] Rusty (accompanied by hints that he was left out in the rain when a baby).
a.1969		‘The Soughrty Peaks’ in G. Logsdon Whorehouse Bells Were Ringing (1995) 131: Sandy Bob and Rusty Jigs, / Had a roundup camp last fall.
1970		E. Thompson Garden of Sand (1981) 482: Rusty, a tall redhead, held up her nails to examine her work.

2. (UK black) a pre-used weapon.

2019

Headie One ‘Rubbery Bandz’ 🎵 See, this rusty cost me couple of grand.