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"parasitic insect infecting human hair and skin," Old English lus, from Proto-Germanic *lus (cf. Old Norse lus, Middle Dutch luus, Dutch luis, Old High German lus, German Laus), from PIE *lus- "louse" (cf. Welsh lleuen "louse"). Slang meaning "obnoxious person" is from 1630s. The plural lice (Old English lys) shows effects of i-mutation. The verb meaning "to clear of lice" is from late 14c.; to louse up "ruin, botch" first attested 1934, from the literal sense (of bedding), from 1931.
Plural of louse.
n. pl. lice (līs)
Any of numerous small, flat-bodied, wingless biting or sucking insects of the orders Mallophaga or Anoplura, many of which are external parasites on humans.
(Heb. kinnim), the creatures employed in the third plague sent upon Egypt (Ex. 8:16-18). They were miraculously produced from the dust of the land. "The entomologists Kirby and Spence place these minute but disgusting insects in the very front rank of those which inflict injury upon man. A terrible list of examples they have collected of the ravages of this and closely allied parasitic pests." The plague of lice is referred to in Ps. 105:31. Some have supposed that the word denotes not lice properly, but gnats. Others, with greater probability, take it to mean the "tick" which is much larger than lice.