Hard, protective coverings made of keratin that grow on the tips of fingers and toes.
From 'finger' (Old English 'finger,' possibly meaning 'one that seizes') combined with 'nail' (Old English 'nægel,' related to words for fastening), literally 'finger-nails' as fasteners.
Fingernails grow about 3 millimeters per month, and you can estimate how old a bruise under your nail is by how far down it is—they're like a physical timeline of your recent accidents.
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