Origin and history of unco

Old English uncuð , of facts, lands, persons, peoples, "unknown, unidentified;" hence "strange, unusual, suspicious; uncertain, unfamiliar;" also "unfriendly, unkind, rough," from un- (1) "not" + cuð "known, well-known," past participle of cunnan "to know" (see can (v.1)).

The meaning "strange and awkward, crude, clumsy" is recorded by mid-15c., perhaps late 14c. Related: Uncouthly; uncouthness. Shortened form unco "strange, unusual" is by early 15c., also unked (c. 1300), etc.

The compound and the notion it describes are widespread in IE languages, such as Latin ignorantem, Old Norse ukuðr, Gothic unkunþs, Sanskrit ajnatah, Armenian ancanaut', Greek agnotos, Old Irish ingnad "unknown."