/ ˌprɒtəˈsteɪʃn; NAmE ˌprɑːt-/ noun
[ C , U ] ( formal ) a strong statement that sth is true, especially when other people do not believe you :
She repeated her protestation of innocence.
Despite his protestation to the contrary, he was extremely tired.
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WORD ORIGIN
Middle English : from Old French , from late Latin protestatio(n-) , from protestari to protest, from pro- forth, publicly + testari assert (from testis witness).