O.E. hund "dog," from P.Gmc. *khundas (cf. Ger. Hund, O.N. hundr, Goth. hunds), from PIE *kuntos, dental enlargement of base *kwon- "dog" (see canine). Meaning narrowed 12c. to "dog used for hunting." The verb sense of "urge on, incite" is first attested 1528, that of "pursue relentlessly" is first recorded 1605.