The story
The popular belief that the word came from French oui (“yes”) + German ja (“yes”) is a misconception. The name is taken from a word spelled out on the board when it was asked to name itself by Helen Peters, sister-in-law of Kennard Company investor Elijah Bond. It is noted in personal letters that Ouija was the name of a woman in a painting above her head at the time, who it is speculated may have in fact been Ouida.
Etymology from Wiktionary, CC BY-SA 4.0.