1560s, "to prejudice;" 1570s, "to judge beforehand," from French préjuger (16c.), equivalent to Latin praejudicare "to judge or decide beforehand;" see pre- + judge (v.). Related: Prejudged; prejudging; prejudgment.
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-.
c. 1200, iugen, "examine, appraise, make a diagnosis;" c. 1300, "to form an opinion about; inflict penalty upon, punish; try (someone) and pronounce sentence," also intransitive, "make a decision, decide, think, suppose;" from Anglo-French juger, Old French jugier "to judge, pronounce judgment; pass an opinion on" (10c., Modern French juger), from Latin iudicare "to judge, to examine officially; form an opinion upon; pronounce judgment," from iudicem (nominative iudex) "a judge," a compound of ius "right, law" (see just (adj.)) + root of dicere "to say" (from PIE root *deik- "to show," also "pronounce solemnly").
Related: Judged; judging. Spelling with -dg- emerged mid-15c. The Old English word was deman (see doom (n.)). The Latin word also is the source of Spanish juzgar, Italian giudicare.
<a href="https://www.etymonline.com/word/prejudge">Etymology of prejudge by etymonline</a>
Harper, D. (n.d.). Etymology of prejudge. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/prejudge