A person or device that attaches or fastens something; someone whose job or function is to attach things.
From attach + '-er' (one who does the action), a standard English agent noun formation, though the word is relatively rare.
In medieval armies and courts, an 'attacher' was actually a royal official—someone who 'attached' or confiscated property on behalf of the king, a word from French legal tradition that mostly vanished when governments changed legal systems.
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