Old English hund "dog," from Proto-Germanic *hundas (cf. Old Saxon and Old Frisian hund, Old High German hunt, German Hund, Old Norse hundr, Gothic hunds), from PIE *kuntos, dental enlargement of root *kwon- "dog" (see canine). Meaning narrowed 12c. to "dog used for hunting."
"hunt with hounds," 1520s, from hound (v.). Sense of "pursue relentlessly" is first recorded c.1600. Related: Hounded; hounding.