'Thief' is purely Germanic — possibly from a root meaning 'to crouch or hide.' An etymological mystery.
A person who steals another person's property, especially secretly and without the use of force.
From Old English 'þēof,' from Proto-Germanic *þeubaz (thief), of uncertain deeper origin. The word is confined to the Germanic family — German 'Dieb,' Dutch 'dief,' Old Norse 'þjófr,' Gothic 'þiufs' — with no agreed cognates outside it. Some scholars have tentatively connected it to PIE *teup- (to crouch, to hide), which would make the thief literally 'the one who crouches or