Where does “ミレニアム” come from?
ミレニアム (Japanese) comes from English millennium, from Late Latin millennium, from Latin -ennium, from Latin -ennis, from Latin annus, from Proto-Italic atnos, from Proto-Indo-European h₂et-no-, from Proto-Indo-European h₂et- — grass.
ミレニアム (Japanese): a millennium
Ancestry of “ミレニアム”, step by step