Green’s Dictionary of Slang

high-hat adj.

also high-hatted
[note Philip ‘Vaudeville’ (in Federal Writers’ Project 1939): ‘“High hat,” another term used in the same sense, is quite obvious. For example: John Juggler, who has been performing in white flannels, or other cheap costume, appears in new wardrobe presenting his act in a full dress suit and top hat, i.e. – a “high hat.” This new ensemble indicates greater prestige, apparent prosperity, and a professional advance. Other vaudevillians, upon commenting upon it might remark: “I see John has gone high hat.”’]

of items and individuals, snobbish, pertaining to the upper-class.

[Aus]Sydney Sportsman (Surry Hills, NSW) 6 Mar. 1/6: There, among the high-hat dandies, / And among the ladies too.
[US] ‘Coffee Grows On White Folks’ Trees’ in T.W. Talley Negro Folk Rhymes 107: So dat yeller gal loves dat high-hat dandy.
[US](con. 1920s) J.T. Farrell Young Manhood in Studs Lonigan (1936) 197: It might make you into a high-hat snob. [Ibid.] 271: Dinny Gorman, the high hat windbag of a politician! [Ibid.] 404: What the hell, Hink never used to be high hat like this.
[US]E. Freeman ‘The Whirling Hub’ in Afro-American (Baltimore, MD) 2 Mar. 15/1: To some, the Challengers are a group of high-hatted intelligentsia.
[UK]G. Kersh Night and the City 88: And when I say: ‘Come along and make yourself a few quid,’ you start going all high-hat.
[US]‘Digg Mee’ ‘Observation Post’ in N.Y. Age 30 Nov. 10/5: Mary Crockett and Irene Davis seem to have gone hi-hat since Sammy Cogdell and Adolph Boone have shown interest in them.
[Aus]D. Stivens Courtship of Uncle Henry 70: ‘Okay,’ I says. ‘I catch on. I’ll serve up the high hat talk.’.
[UK]K. Howard Small Time Crooks 13: It was no high-hat joint, but a sight smarter than anything icky was used to. [Ibid.] 62: Rose Flaherty was not the sort of dame to get high-hat just because a man looked at her.
[US]R.M. Dashwood Provincial Daughter (2002) 25: Take instant dislike to Mrs Senna, and think she sounds very high-hat.
Charles Petrie A Historian Looks at His World 89: As AP Herbert once put it, there was nothing ‘high-hat’ about him.
Jack Ritchie Tiger Island 120: They were all in the contracting business or trucking or unions and nobody was at all high hat.