Green’s Dictionary of Slang

1. the act of working as a beggar, a cadger or a begging-letter writer pretending to be a gentleman fallen on hard times; usu. as on the high fly.

1839		W.A. Miles Poverty, Mendicity and Crime; Report 146: Going the high-fly is playing the part of a broken-down gentleman, without selling anything. [Ibid.] 156: He draws up fakements for the high-fly, at the padding kens. [...] The padding ken [...] is full of prigs and shallow chaps and fellows on the high-fly.
1857		‘Ducange Anglicus’ Vulgar Tongue 39: The padding ken [...] is full of prigs and shallow chaps and fellows on the high-fly.
1860		Hotten Dict. of Modern Sl. etc. (2nd edn) 154: High-fly ‘on the HIGH-FLY,’ on the begging or cadging system.
1874		Derbyshire Courier 12 Dec. 7/1: Local Flash language [...] high-fly, the - begging letters.
1882		Sydney Sl. Dict. 10/2: The Parson is on the highfly in a fantail banger and a milky mill tog. He got the cant of togs from a shickster whose husband’s in a bone-box. He’ll gammon the swells. He touched one for an alderman the first ten minutes.
1895		Crowe Aus. Sl. Dict. 36: High-Fly, a genteel begging letter.

2. showing off, acting in a superior, arrogant manner.

1906		E. Pugh Spoilers 58: Come off! [...] Not so much o’ the high-fly!
1912		E. Pugh City Of The World 239: And clobbered up all gay right through [...] And doin’ the high-fly on weekdays as well.