Any moth of the family Lasiocampidae, characterized by hairy caterpillars and tent-like cocoons.
From the 'egg' appearance of the caterpillar cases or possible folk etymology. Related to 'egger.' The term has been used in English entomology since at least the 17th century.
These moths get their strange name because their cocoons look like lumpy egg cases hung in trees—medieval naturalists were very literal with their naming!
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