Asinine

google

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late 15th century: from Latin asininus, from asinus ‘ass’.

wiktionary

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From Latin asinīnus(“of a donkey or ass”).

etymonline

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asinine (adj.)

c. 1600, "obstinate, stupid, offensively silly," from Latin asininus "stupid," literally "like an ass," from asinus "ass," also "dolt, blockhead" (see ass (n.1)). The literal sense in English is recorded from 1620s. Related: Asininity.