According to the OED, the term is borrowed from the Banyans in the East Indies, a caste that eat nothing that had life.
banyan day (plural banyan days)
- (dated, nautical, idiomatic) In British naval tradition, this originally referred to a day of the week when galley kitchens served no meat on board ship.
- (idiomatic) In modern usage it refers to a picnic or cookout for the ship's crew.
Last modified on 16 June 2013, at 23:34