A person who avows or openly declares something; someone making an avowal.
From 'avow' plus the agent suffix '-er' (one who performs the action), following the standard English pattern for creating agent nouns.
In legal history, avowers were brave (or reckless) people who would stand up in court and claim responsibility, putting their reputation and sometimes their life on the line. The word respects their courage even if we disagree with their cause.
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