Witless

wiktionary

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From Middle English witles, from Old English witlēas(“senseless; witless”), from Proto-Germanic *witjalausaz(“witless”), equivalent to wit +‎ -less. Cognate with Swedish vettlös(“senseless; witless; wild”), Icelandic vitlaus(“senseless; witless; foolish; mad”).

etymonline

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witless (adj.)

Old English witleas "foolish, mad;" see wit (n.) + -less. Phrase scared witless attested from 1975. Related: Witlessly; witlessness.