The definition of a caterpillar is the wormlike larvae of a moth or a butterfly.(noun)
A little hairy worm-like animal that will build a cocoon and eventually become a butterfly is an example of a caterpillar.
See caterpillar in Webster's New World College Dictionary
Origin: ME catirpel < NormFr catepilose (OFr chatepelose), lit., hairy cat < L catta, cat + pilosus < pilus, hair: see pile
See caterpillar in American Heritage Dictionary 4
Origin: Middle English catirpel, catirpeller
Origin: , probably alteration of Old North French *catepelose
Origin: : cate, cat (from Latin cattus)
Origin: + pelose, hairy (from Latin pilōsus; see pilose). Word History: Larvae of moths and butterflies are popularly seen as resembling other, larger animals. Consider the Italian dialect word gatta, “cat, caterpillar”; the German dialect term tüfelskatz, “caterpillar” (literally “devil's cat”); the French word chenille, “caterpillar” (from a Vulgar Latin diminutive, *canīcula, of canis, “dog”); and last but not least, our own word caterpillar, which appears probably to have come from an unattested Old North French word *catepelose, meaning literally “hairy cat.” Our word caterpillar is first recorded in English in 1440 in the form catyrpel. Catyr, the first part of catyrpel, may indicate the existence of an English word *cater, meaning “tomcat,” otherwise attested only in caterwaul. Cater would be cognate with Middle High German kater and Dutch kater. The latter part of catyrpel seems to have become associated with the word piller, “plunderer.” By giving the variant spelling -ar, Johnson's Dictionary set the spelling caterpillar with which we are familiar today.
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