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-.
early 15c., "train of followers," from Old French sequelle (14c.), from Late Latin sequela "that which follows, result, consequence," from sequi "to follow, come after, follow after, attend, follow naturally," from PIE root *sekw- (1) "to follow." Meaning "consequence" is attested from late 15c. Meaning "story that follows and continues another" first recorded 1510s.
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Harper, D. (n.d.). Etymology of prequel. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/prequel