1520s, "marked by misfortune or failure," from un-(1) "not" + lucky, adj.. Similar formation in West Frisian unlokkich, Mliddle Low German unluckich. Sense of "boding ill" is recorded from 1540s; that of "having bad luck" is from 1550s; that of "bringing bad luck" is from 1580s. Related: Unluckily; unluckiness.