sleuth /sluːθ/ BrE AmE noun [countable] old-fashioned
[ Date: 1800-1900 ; Origin: sleuthhound 'dog used for tracking people' (14-20 centuries) , from sleuth 'track' (12-15 centuries) (from Old Norse sloth ) + hound ]
someone who tries to find out information about a crime SYN detective
—sleuthing noun [uncountable]