premillennial (adj.)

1660s, "pertaining to the millennium," from stem of millennium + -al (1). Meaning "pertaining to a period of 1,000 years" is from 1807. As a noun from 1896, originally "a thousandth anniversary." From 1991 as a generational name for those born in the mid-1980s and thus coming of age around the year 2000.

word-forming element meaning "before," from Old French pre- and Medieval Latin pre-, both from Latin prae (adverb and preposition) "before in time or place," from PIE *peri- (source also of Oscan prai, Umbrian pre, Sanskrit pare "thereupon," Greek parai "at," Gaulish are- "at, before," Lithuanian prie "at," Old Church Slavonic pri "at," Gothic faura, Old English fore "before"), extended form of root *per- (1) "forward," hence "beyond, in front of, before."

The Latin word was active in forming verbs. Also see prae-. Sometimes in Middle English muddled with words in pro- or per-.