masc. proper name, literally "fair-haired," from Old English scir "bright" (see sheer (adj.)) + locc "lock of hair" (see lock (n.2)). Slang for "private detective, perceptive person" (the latter often ironic) is attested by 1903, from A.C. Doyle's fictional character Sherlock Holmes (the character's full name in this sense was so used from 1896; Holmes debuted in 1887 and was popular by 1892).
updated on August 21, 2022