A caterpillar is the long, worm-like stage of a butterfly or moth before it changes into its adult form. It usually has many small legs and eats a lot of leaves to grow.
From Middle English 'catyrpel' or 'catepelose', likely from Old French 'chatepelose' meaning 'hairy cat', from 'chat' (cat) and 'pelose' (hairy). People named it after its fuzzy, cat-like appearance.
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