omen.

From Old Latin osmen, of uncertain origin, with many origins proposed: * Ancient authors derived it from ōs (“mouth”). * Derived from Proto-Indo-European *h₂ew- (“to see, perceive”), whence audiō and Ancient Greek οἴομαι (oíomai, “to think, believe, suppose”). * Per Beneviste and Oettinger, connected to Hittite [script needed] (hā-ᶻᶦ, “to believe, trust”) via a supposed Proto-Indo-European *h₂e/oh₃-s-mn (“trust”). De Vaan considers this semantically unconvincing. * Per De Vaan (who doubts the authenticity of the Old Latin form osmen), most likely from Proto-Italic *okʷsmn- (“sighting, omen”), from an s-present form of Proto-Indo-European *h₃ekʷ- (“to see; eye”) + *-men (whence -men). * An alternative theory by Meier-Brügger derives the word from Proto-Indo-European *Hoǵ-smen (“speech, what was predicted”), from an o-grade of Proto-Indo-European *h₁eǵ- (“to say”) (whence aiō (“id”)). This is semantically attractive, but requires the existence of the otherwise unattested-in-Latin o-grade of aiō, as well as an atypical formation of a smen-derivative from the Proto-Indo-European perfect *He-Hoǵ-.