Green’s Dictionary of Slang

a lady, a gentleman; also as adj.

[1873		Sl. Dict. 274: Rye Gipsy term for a young woman. In the same parlance ‘rawnie’ is a young woman].
1936		J. Curtis Gilt Kid 233: She would have to give up that rye mort touch.
1938		J. Curtis They Drive by Night 219: ‘Sit comfy. Like a gentleman.’ ‘Blimey, bloody fine rye mush I’d make.’.
1950		P. Hoskins No Hiding Place! 191/2: Rye Mush. A man with tone .