Etymology of thief by etymonline (original) (raw)

Old English þeof "one who takes property from another by stealth; a robber," from Proto-Germanic *theuba- (source also of Old Frisian thiaf, Old Saxon thiof, Middle Dutch and Dutch dief, Old High German diob, German dieb, Old Norse þiofr, Gothic þiufs), a word of uncertain origin.

In Middle English also of poachers, cheats, pirates, braggarts, usurers, a general term of reproach for lawless and deceitful persons. Den of thieves "abode of the lawless" is from late 14c. (dennes of þeves), the earlier phrase was thieves' ditch (theovesdiches, c. 1100).

A thief takes other people's property without their knowledge ; a robber takes it openly, whether or not resistance is offered : in a looser sense, thief is often applied to one who takes a small amount, and robber to one who takes a large amount. [Century Dictionary, 1895]