Green’s Dictionary of Slang

1. a generic name for any Scot.

1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue.
1810		C. Dibdin Yngr Spectre Knight 15: Sandy Grey was a bit of a ranter, O, he was the Highlander gay.
1841		‘Hurrah For An Irish Stew’ Dublin Comic Songster 100: Here’s health to John Bull and his beef, / Here’s health to Sandy and brew, / Here’s a health to Paddy, good luck, and in brief, / Success to his Irish stew.
1857		Londonderry Standard 7 May 4/1: Alexander, or, as he was invariably called, Sandy Miller.
1866		‘Irish Church Question’ in C. Hindley Curiosities of Street Lit. (1871) 84: The sandys danced tullochgorum round the rims of their porridge-pots.
1873		Sportsman (London) ‘Notes on News’ 10 May 4/1: Well done, Brither Sandy.
1885		Bulletin (Sydney) 11 Apr. 12/2: The Corporation at Inverell called tenders for some work, and in due time the local Sandys met to consider them. Donald M’Kenzie’s was the lowest, and this just suited the local Sandy’s; but when Donald turned out to be a Chinaman, they thought another half Scotchman in Australia was too much for them.
1890		Bulletin (Sydney) 16 Aug. 14/3: The Christian Colonist has taken the trouble to learn that of lunatics in N.S.Wales last year 1301 were Roman Catholics and 218 were Presbyterians. Very naturally. ‘wit to madness near allied’ is found more often in Paddy than in Sandy.
1896		Regiment 18 July 242/1: Sandy losing all patience, thrust his bonnet out on the point of his bayonet.
1900–10		Stephens & O’Brien Materials for a Dict. of Aus. Sl. [unpub. ms.] 135: SANDY: slang generic name for Scotchmen as Paddy is for Irishmen.
1913		Williams & Godfrey [perf. Billy Williams] ‘All the ladies fell in love with Sandy’ 🎵 Sandy was a hielan’ man / Quite a dandy hielan' man.
1926		J. Doone Timely Tips For New Australians 9: They point out that the world over an American is styled a ‘Yank,’ an Irishman a ‘Mick,’ a Scotchman ‘Sandy,’ and so forth.
1927		‘J.M. Hall’ Anecdota Americana I 103: A Scotchman was observed, riding up and down the White Way, on a horse. But Sandy, instead of facing front had seated himself so that he faced the horse’s tail.

2. see Sandy Macnab n. (2)