From the avatar wiki:

The term “Avatar” comes from the Sanskrit word avatāraḥ (अवतारः), which means “descent”. In Hinduism, Vishnu manifests himself as an avatar to restore balance on earth, during a period of imbalance.

And there’s a lot of overlap with Hindi Avatars in general: https://en.m.wikipedia.org/wiki/Avatar.

So pretty apt if you ask me