A person who darns clothes, or a dragonfly (because of its resemblance to a needle used for darning).
From 'darn' plus the agent suffix '-er,' meaning 'one who darns.' The dragonfly meaning emerged from folk etymology due to the insect's needle-like appearance and rapid movements resembling sewing motions.
Darning needles were the original name for dragonflies, but it's completely wrong—dragonflies don't darn anything! People just thought they looked like sewing needles, and the nickname stuck for over 200 years.
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