The Ancient Greek word “δαίμων” referred to a lesser god linked to a place (like the spirit of the hearth) or a person (like a guardian angel). Latin took this idea into the related word “genius” which in modern Romance languages can mean either an intelligent person or a person’s mood. In Spanish, “estar de mal genio” means “to be in a bad mood”. So then to have “ευδαιμονία” can mean “to be in a good mood” although it’s probably meant to be more permanent than that.
I am reminded of the name of Othello's wife, Desdemona, which shares a similar etymology (in fact they are antonyms of one another). The sense is "ill-fated" [0]
See:
https://en.wiktionary.org/wiki/δαίμων#Ancient_Greek
https://en.wikipedia.org/wiki/Genius_(mythology)