A person who apologizes or expresses regret (American spelling); also one who defends or justifies.
From apologize (American form) + -er agent suffix. The verb apologize comes from Greek apologia via French apologie, shifted from the 'defend' sense to 'express regret' in modern usage.
Interestingly, the oldest meaning of 'apologize' was to defend yourself (like in court), but by the 1600s it shifted to mean expressing regret—a complete reversal that shows how language can flip meanings entirely.
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