month

Month comes from Old English mōnaþ, from Proto-Germanic *mēnōþs, tracing back to Proto-Indo-European *mḗh₁n̥s, meaning 'moon, month.' That root likely grew from *meh₁-, meaning 'measure' — since the moon's cycle was used to measure stretches of time.

The word has stayed remarkably close to its roots: it simply named a unit of time tied to the moon's cycle, and it still does. It also pushed out a rival: Old English once used calend, borrowed from Latin calendae, but month won out.

Month is directly related to moon — both descend from the same Proto-Indo-European root meaning 'moon,' since counting moons was how people first measured longer spans of time.