Meaning of water louse in English:
water louse
noun
Any of various aquatic insects and crustaceans; (in later use) especially any isopod crustacean of the genus Asellus, the members of which resemble woodlice.
Origin
Late 17th century; earliest use found in James Chetham (bap. 1640, d. 1692), writer on angling.
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