Ominous

google

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late 16th century: from Latin ominosus, from omen, omin- ‘omen’.

wiktionary

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From Latin ominosus(“full of foreboding”), from omen(“forbidden fruit, omen”), from os(“the mouth”) + -men.

etymonline

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ominous (adj.)

"conveying an omen, significant," 1580s, from Latin ominosus "full of foreboding," from omen (genitive ominis) "foreboding" (see omen (n.)). Especially (and now exclusively) "of ill omen, giving indication of coming evil." Related: Ominousness.