to renounce (esp a claim, opinion, or allegiance) on oath, solemnly, or formally
As solemnly as I took his name, I now abjure it — Mary Wollstonecraft
abjuration /abjəʹraysh(ə)n/ noun
abjurer noun
[Middle English abjuren via French from Latin abjurare, from ab- + jurare: see jury1]