Green’s Dictionary of Slang

a meaningless or vaguely contemptuous and ultimately childish retort, responding to a speaker who has made the offensive comment, ‘You’re a...’.

1550		Udall Ralph Roister Doister V iii: roister: If it were another than but thou, it were a knave. m. merry: Ye are another your self, sir, the Lord us both save.
1569–70		T. Preston Cambyses E: And thou callst me knave thou art another.
1749		Fielding Tom Jones (1959) 317: I did not mean to abuse the cloth; I only said your conclusion was a nonsequitur.’ – ‘You are another,’ cries the sergeant.
1836–7		Dickens Pickwick Papers (1999) 201: ‘Sir,’ said Mr Tupman, ‘you’re a fellow.’ ‘Sir,’ said Mr Pickwick, ‘You’re another.’.
1873		J.H. Beadle Undeveloped West 48: A furious rivalry raged between the city and Council Bluffs on the eastern side of the Missouri; pretty much in the ‘You’re another!’ style of argument.
1881		Bulletin (Sydney) 14 May. 2/2: Mr. Reid has in him all the potentialities of a moderately useful public man, but if he cannot conduct an argument without calling out ‘You’re another,’ he may bid farewell to fame.
1885		Sat. Rev. (London) 26 Mar. in Ware (1909) 10/1: It seems a pity that the Whitehall Review did not confine itself to saying, in the speech of ’Arrydom, ‘You’re another’ instead of appealing to a special jury.
1890		London Dly News 1 Feb. 4/7: ‘You’re another’ is hardly polished, yet it is not without dignity, for it has been rude for nearly three hundred and fifty years.
a.1891		J.R. Lowell Democracy n.p.: I find little to interest and less to edify me in these international bandyings of you’re another [F&H].
1900		Bulletin (Sydney) 3 Feb. 13/2: Tommy Atkins (to stranger): ‘[...] I know what you would like – why, to be a soldier bold, and go fight the Boers. Now, wouldn’t you?’ / Stranger: ‘You’re another! I’m waiting for the blanky tram, that’s all.’.
1949		N.Y. Herald Trib. 28 Aug. II 7/1: [cartoon caption] You’re another!