Bloodhound

wiktionary

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From Middle English blodhound, blodhond; equivalent to blood +‎ hound. Cognate with Dutch bloedhond(“bloodhound”), Middle Low German blōthunt(“bloodhound”), German Bluthund(“bloodhound”), Danish blodhund(“bloodhound”), Swedish blodhund(“bloodhound”). The detective sense follows from the dog's ability to follow a trail.

etymonline

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bloodhound (n.)

also blood-hound, type of large dog used in hunting, c. 1300, from blood (n.) + hound (n.). It traces wounded prey by the scent of the blood it has spilled, or any other trace. Similar formation in Dutch bloedhond, German Bluthund.