noun (n)

• someone who admits or acknowledges openly and boldly(noun.person)

  source: wordnet30
• someone who claims to speak the truth(noun.person)

  Example:
  An avower of his own great intelligence.
  

  Synonym:
  affirmer, asserter, asseverator, declarer
  

  source: wordnet30
• One who avows or asserts.(noun)

  source: webster1913