from nab (n.) one who nabs, a police officer (slang)
From: The Spirit of the Public Journals for the Year M.DCCC.XXIII (1823)
Being an Impartial Selection of the Most Exquisite Essays, Jeux D'esprit, and Tales of Humour, Prose and Verse, that have appeared in the
Morning, Evening, and Sunday Newspapers.
By George Cruikshank, 1824