1640s, of plants or leaves, "evergreen" (a sense now obsolete), formed in English from Latin perennis "lasting through the year (or years)," from per "through" (from PIE root *per- (1) "forward," hence "through") + annus "year" (see annual (adj.)). The botanical sense of "remaining alive through more than two years" is attested from 1670s; of springs, etc., "lasting or continuing without cessation through a year or many years," by 1703. The figurative meaning "enduring, permanent" is from 1750. Related: Perennially. For vowel change, see biennial. The noun meaning "a perennial plant" is from 1763.
