"solemn renunciation," mid-15c., originally of heresy or idolatry, later of renunciations of oaths generally, from Latin abiurationem (nominative abiuratio) "a denying on oath," noun of action from past-participle stem of abiurare "deny on oath," from ab "off, away from" (see ab-) + iurare "to swear," from ius (genitive iuris) "law" (see jurist). Related: Abjuratory. The oath of abjuration is "the negative part of the oath of allegiance" [Century Dictionary].