One who forbears; a person who shows patience or restraint.
From 'forbear' + '-er' (one who does). The '-er' suffix is one of the oldest in English, going back to Old English '-ere.'
The '-er' suffix is so old and productive that we barely think about it—we add it to almost any verb to get 'someone who does that thing,' creating words like runner, teacher, and forbear-er.
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