The act of folding and sewing the edge of fabric to finish it and prevent fraying; can also mean hesitating or pausing in speech (hemming and hawing).
From Old English 'ham' (to fold), with '-ing' as a gerund suffix; the speech meaning may derive from the 'hm' or 'hmm' sounds people make when hesitating.
The phrase 'hemming and hawing' comes from imitating the sounds of hesitation, but the 'hem' part is a real sewing term—language mixes its metaphors from completely different domains!
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