Green’s Dictionary of Slang

an aggressive reply to a questioner implying that whatever the answer may be, it is none of their business.

c.1625		Webster Cure for a Cuckold III ii: If I be horn-mad, what’s that to you?
1671		‘L.B.’ New Academy of Complements 259: But yet I fear my Jenny’s face, / Will cause more men to woo, / Which I shall take for a disgrace, / But what’s that to you?
1673		T. Shadwell Epsom Wells IV i: mrs bisk: Where have you been, you Fop Doodle? bisk: What’s that to you Jilt-Flirts?
1712		J. Arbuthnot Hist. of John Bull 60: John would jeer her. ‘What think you of my sister Peg (says he) that faints at the sound of an organ, and yet will dance and frisk at the noise of a bag-pipe?’ ‘What’s that to you, Gundy-guts (quoth Peg), every body’s to chuse their own musick.’.
1733		Fielding Don Quixote I vi: What is it to you what we are, Saucebox?
1738		Proceedings at Assizes (Surrey) 9/2: He hearing what she said, says D—n you, what’s that to you.
1797		(con. 1720) J. Holliday Life of William Earl of Mansfield 2: The school-boy’s smart answer rather surprized her ladyship, ‘What is that to you!’.
1837		R. Nicholson Cockney Adventures 4 Nov. 3: What’s it to you, Mother Cockahoop! [...] You’re only wild cos they didn’t take no notice ov you, I s’pose.
1856		M. Griffith Autobiog. of a Female Slave 96: Yes, but what’s it to you, Amy?
1858		F.W. Farrar Eric I 25: What’s that to you? I’ll kick you too, if you say much.
1880		G.F. Northall ‘Momus’ Misc. 34: ‘What do you want here?’ said the gentleman. ‘What’s that to you?’ responded Cade.
1896		Ade Artie (1963) 71: ‘What is your name, Claudie?’ ‘What’s it to you?’.
1901		S.E. White Westerners 131: ‘What’s it to yuh?’ he asked malevolently.
1913–14		E. O’Neill The Web in Ten ‘Lost’ Plays (1995) 63: What’s it to you?
1929		E. Booth Stealing Through Life 65: ‘Trying to pick up some broads?’ He leered at me. ‘What’s it to you?’ I resented his intrusion.
1939		J. Steinbeck Grapes of Wrath (1951) 147: ‘What’s that to you?’ Mae said fiercely.
1945		‘Henry Green’ Loving (1978) 115: ‘What’s it to you?’ he asked though I could see he was ashamed.
1952		J. Jones From Here to Eternity (1998) 519: ‘Maybe I like it,’ Stark said. ‘Whats it to you?’.
1967		R. Conot Rivers of Blood 231: I’m gonna climb a tree and go ape [...] What’s it to you?
1971		B. Malamud Tenants (1972) 31: ‘Are you through for the day?’ ‘What’s it to you?’.
1986		A. Bleasdale No Surrender 17: Why? What’s it to you?
1995		I. Rankin Let It Bleed 80: ‘What’s it to you?’ Her cheeks were reddening with anger.
2000		M. Dibdin Thanksgiving 61: ‘How long does it take to make a john come?’ ‘What’s it to you?’.
2009		J. Joso Soothing Music for Stray Cats 98: ‘What’s it to you?’ I didn’t answer.