Green’s Dictionary of Slang

(US) an important person, a pretentious person.

1800		G. Colman Yngr Heir at Law V ii: But have you heard nothing yet of the high tone, my lord.
1812		G. Colman Yngr ‘Two Parsons’ in Poetical Vagaries 136: All the Ladies of high Ton, and Taste, Titter’d, and turn’d aside.
1876		M. Bornemann Madame Jane Junk 66: [title] Meeting with Hightoners [DA].
1886		‘Lady Kate, the Dashing Female Detective’ in Roberts et al. Old Sleuth’s Freaky Female Detectives (1990) 14/2: He’s a high-toner; only goes in on heavy jobs.
1890		Illus. Police News 5 Apr. 1: [pic. caption] HIGH JINKS AMONG YOUNG HIGH DADDIES OF THE HUB / A Private Party Charter a Suburban Hotel Near Boston / FASHIONABLE HIGH TONES AND THEIR GIRL COMPANIONS GO IT GAYLY.
1945		A. Kober Parm Me 47: Oh, awright, Miss High Tone. I won’t be common.