Definition & Meaning of "lagniappe"in English

What does "lagniappe" mean in Louisiana slang?

The structure is a simple noun borrowed from Louisiana French, which in turn came from Spanish "la ñapa" (the gift or extra), ultimately from Quechua "yapa" (something added). It is used in Louisiana, especially New Orleans and Cajun regions, to describe a small bonus or extra gift given unexpectedly by a merchant to a customer, such as an extra donut in a dozen or a free drink with a meal. People typically say "The baker threw in a lagniappe with my order" or "That little lagniappe made my day."