The holiday of Kwanzaa was created in 1966 by Black Panther activist Maulana Karenga as a way to bring together the African American community. To do this, he examined various African harvest celebrations and tried to make sort of an amalgam of those cultural holidays. Karenga called this combo-holiday kwanza, a word taken from the phrase matunda ya kwanza, meaning "first fruits" in Swahili. He then tacked on an extra a so the word could have seven letters, each representing one of the Seven Principles of Blackness. Now, in that phrase, kwanza was the part meaning "first", so it's really not that surprising that it's the infinitive of a word meaning "to begin", anza. Further etymology is unknown, but, being from a Bantu language, anza could likely trace to a Niger-Congolese ancestor. Usage of the word Kwanzaa peaked in the late 90s, and Google searches for the term always have a seasonal uptick in December.
Adam Aleksic, a rising sophomore studying linguistics and government at Harvard University, has been described as the internet's sixth most famous etymologist. He also has disturbing interests in politics, vexillology, geography, board games, conlanging, and law.