(in Shakespeare's tragedy so called). A Moor, commander of the Venetian army, who eloped with Desdemona. Brabantio accused him of necromancy, but Desdemona, being sent for, refuted the charge. The Moor, being then sent to drive the Turks from Cyprus, won a signal victory. On his return, Iago played upon his jealousy, and persuaded him that Desdemona intrigued with Cassio. He therefore murdered her, and then stabbed himself.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894