protestation (n.)

mid-14c., protestacioun, "affirmation;" late 14c., "avowal, a solemn or formal declaration or assertion," from Old French protestacion "protest, protestation" (13c.) and directly from Late Latin protestationem (nominative protestatio) "a declaration, protestation," noun of action from past-participle stem of Latin protestari "declare publicly, testify, protest" (see protest (n.)). By 1640s as "solemn or formal declaration of dissent."