"to catch (someone)," 1680s, probably a variant of dialectal nap "to seize, catch, lay hold of" (1670s, now surviving only in kidnap), which possibly is from Scandinavian (compare Norwegian nappe, Swedish nappa "to catch, snatch;" Danish nappe "to pinch, pull"); reinforced by Middle English napand "grasping, greedy." Related: Nabbed; nabbing. Nabbing-cull was old slang for "constable," and Farmer & Henley has "TO NAB THE STIFLES = to be hanged."