early 15c., "not uttered in a song," from un- (1) "not" + past participle of sing (v.). Similar formation in German ungesungen. Meaning "not celebrated" is recorded from 1660s.
unsung heroes of the war
unsubstantiated
unsuccessful
unsuitable
unsuited
unsullied
unsung
unsupervised
unsupported
unsure
unsurmountable
unsurpassable