colloquial shortening of tonight, attested by 1918.
Present-day student notices on bulletin boards, etc., read oftener than not, "Party Friday Nite," "Meeting Tonite," "Kum Tonite," etc. [Louise Pound, "Spelling-Manipulation and Present-Day Advertising," Dialect Notes, 1923]
tonite (n.)
explosive used in blasting, 1881, from Latin tonare "to thunder" (see thunder (n.)) + -ite (2).
tongueless
tongue-twister
tonic
tonify
tonight
tonite
tonnage
tonne
tonneau
tonsil
tonsillectomy
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