Green’s Dictionary of Slang

a one-eyed person.

1877		Proc. Old Bailey 28 May 80: You one-eyed gunner, we will knock your other eye out if you don't get in.
1880		D.W. Barrett Life and Work among Navvies 49: If a poor fellow has the misfortune to lose an eye, he gains the name of ‘Gunner’.
1896		G.F. Northall Warwickshire Word-Book 100: Gunner. A one-eyed person.