jacklight

Etymology

* jack + light. Probably from jack (“a male servant of any rank”), later associated with a boy servant or any boy, and later still with a knave: a rogue, thief, or deceitful man. * Possibly also related to Spanish jaque (“a bully”).

noun

1. (Canada, US) A spotlight or lamp mounted on a car.
   It was a long, low roadster, with a jacklight. 1931, William Faulkner, Sanctuary, Library of America, published 1985, page 19

verb

1. (hunting, US, Canada) To shine a jacklight or spotlight on an animal, usually a deer, to aid in hunting at night.