Alegre, Spanish for happiness, has a close English cousin in alacrity (an SAT word meaning “eagerness” or “cheerful readiness”).
Both come from the Latin alacritas meaning the same as the English.
It’s funny, to me at least, how the word for eagerness turned into the word for happy in Spanish: there is a strong and ancient correlation between being willing to do things, and excited about them — and being happy.