Lagniappe \LAN-yap\ , noun;
1. A small gift given with a purchase to a customer, for good measure
2. A gratuity or tip
3. An unexpected or indirect benefit
This word, with the meaning "dividend, something extra," dates to 1849 and comes from New Orleans Creole. Originally it was a bit of something New Orleans shopkeepers would give to customers. It's origin in Creole is speculative; it's probably from American Spanish la ñapa ("the gift"), possibly with influence from Quechua yapa ("something added, gift").
Today's word and the first definition were both taken from Dictionary.com's 'Word of the Day' for Wednesday, December 22
Etymologies come from the Oxford English Dictionary and/or Etymonline.com