1570s, "the consequence of anything" (as in in the event that); 1580s, "that which happens;" from French event, from Latin eventus "occurrence, accident, event, fortune, fate, lot, issue," from past participle stem of evenire "to come out, happen, result," from assimilated form of ex- "out" (see ex-) + venire "to come" (from a suffixed form of PIE root *gwa- "to go, come"). Meaning "a contest or single proceeding in a public sport" is from 1865. Events as "the course of events" is attested from 1842. Event horizon in astrophysics is from 1969.
"returning from time to time, reappearing, repeated," 1660s, from French recurrent (16c.) and directly from Latin recurrentem (nominative recurrens), present participle of recurrere "run back, hasten back, return" (see recur). From 1590s as a noun ("recurrent artery or nerve," one turned back on itself).
in rhetoric, "comparison, metaphor," according to Century Dictionary, "especially a formal simile, as in poetry or poetic prose, taken from a present or imagined object or event: distinguished from a paradigm, or comparison with a real past event," 1580s, from Greek parabolē "comparison" (see parable).
as an annual ecological awareness event on April 22, from 1970; the idea for it and the name date from 1969.