Lagniappe

lagniappe \ˈlan-ˌyap\ noun: 1. a small gift given a customer by a merchant at the time of a purchase, 2. broadly, something given or obtained gratuitously or by way of good measure

Etymology: American French, from American Spanish la ñapa the lagniappe, from la + ñapa, yapa, from Quechua yapa something added

Merchant gifting happens all the time, yet I never hear anyone use the term lagniappe to name it.