future

Future comes from Middle English future, from Old French futur, from Latin futūrus — the irregular future active participle of sum, "to be," itself from Proto-Indo-European *bʰuH-, "to become, be."

The Latin word simply meant "about to be," the natural future tense of the verb "to be"; it passed through Old French and into Middle English largely intact in meaning, as the noun and adjective for time yet to come.

It's a doublet of "futur," and cognate with Old English bēo, ancestor of "be" — so "future" and "be" are, at root, the same idea of existing. English once had its own word for this concept, tōweard, which survives today as "toward," its meaning having drifted elsewhere; Middle English also briefly used afterhede, literally "afterhood."