bloodhound

• blood-hound
• bloudhound, bloud-hound (both obsolete)

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.

• (UK) IPA^(key): /ˈblʌd.haʊnd/

bloodhound (plural bloodhounds)

1. A large scenthound famed for its ability to follow a scent many days old, over vast distances. This dog is often used as a police dog to track missing people, fleeing suspects, or escaped prisoners.
2. (figurative) A detective or other person skilled at finding people or clues.
3. (archaic) A bloodthirsty person.
   • 1817 December, Percy Bysshe Shelley, “The Revolt of Islam. […]”, in [Mary] Shelley, editor, The Poetical Works of Percy Bysshe Shelley. […], volume I, London: Edward Moxon […], published 1839, →OCLC, page 263:

     For now the despot’s blood-hounds with their prey,
     Unarmed and unaware, were gorging deep
     Their gluttony of death; the loose array
     Of horsemen o’er the wide fields murdering sweep,
     And with loud laughter for their tyrant reap
     A harvest sown with other hopes; […]

• bloodhoundish