1660s (Milton), from Latin iubilantem (nominative iubilans), present participle of iubilare "to let out whoops," in Christian writers, "to shout for joy," related to iubilum "wild shout," from Proto-Italic *iu, an exclamation of joy that probably was in Proto-Indo-European (cognates: Greek iu, an interjection of amazement, iuge "crying;" Middle High German ju, juch, an exclamation of joy; Dutch juichen, Old Norse yla, English yowl). With ending as in sibilant. Related: Jubilantly.