early 14c. (attested from late 12c. in Anglo-Latin), from Anglo-French juree (late 13c.), from Medieval Latin iurata "an oath, an inquest," fem. past participle of Latin iurare "to swear," from ius (genitive iuris) "law" (see jurist). Meaning "body of persons chosen to award prizes at an exhibition" is from 1851. Grand jury attested from early 15c. in Anglo-French (le graund Jurre).
"temporary," 1610s, in jury-mast, a nautical term for a temporary mast put in place of one broken or blown away, of uncertain origin. The word perhaps is ultimately from Old French ajurie "help, relief," from Latin adjutare (see aid (n.)).