jubilant adj.

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.