Mouth
Old English mūth, of Germanic origin; related to Dutch mond and German Mund, from an Indo-European root shared by Latin mentum ‘chin’.
wiktionary
From Middle English mouth, from Old English mūþ(“mouth, opening, door, gate”), from Proto-West Germanic *munþ, from Proto-Germanic *munþaz(“mouth”), from Proto-Indo-European *ment-(“to chew; jaw, mouth”). Cognate with Scots mooth(“mouth”), North Frisian müd, müth, müss(“mouth”), West Frisian mûn(“mouth”), Dutch mond(“mouth”), muide(“river mouth”) and mui(“riptide”), German Mund(“mouth”), Swedish mun(“mouth”), Norwegian munn(“mouth”), Faroese muður, munnur(“mouth”), Icelandic munnur(“mouth”), Gothic 𐌼𐌿𐌽𐌸𐍃( munþs, “mouth”), Latin mentum(“chin”) and mandō(“to chew”), Ancient Greek μάσταξ(mástax, “jaws, mouth”) and μασάομαι(masáomai, “to chew”), Albanian mjekër(“chin, beard”), Welsh mant(“jawbone”), Hittite[script needed](mēni, “chin”).
The verb is from Middle English mouthen, from the noun.
etymonline
mouth (n.)
Old English muþ "oral opening of an animal or human; opening of anything, door, gate," from Proto-Germanic *muntha- (source also of Old Saxon, Old Frisian muth, Old Norse munnr, Danish mund, Middle Dutch mont, Dutch mond, Old High German mund, German Mund, Gothic munþs "mouth"), with characteristic loss of nasal consonant in Old English (compare tooth), probably an IE word, but the exact etymology is disputed. Perhaps from the source of Latin mentum "chin" (from PIE root *men- (2) "to project," on the notion of "projecting body part"), presuming a semantic shift from "chin" to "mouth."
In the sense of "outfall of a river" it is attested from late Old English; as the opening of anything with capacity (a bottle, cave, etc.) it is recorded from mid-13c. Mouth-organ attested from 1660s. Mouth-breather is by 1883. Mouth-to-mouth "involving contact of one person's mouth with another's" is from 1909.
Word of mouth "spoken words, oral communication" (as distinguished from written words) is by 1550s. To put words in (someone's) mouth "represent as having said what one did not say" is from late 14c.; to take the words out of (someone's) mouth "anticipate what one is about to say" is from 1520s. To be down in the mouth "dejected" (1640s) is from the notion of having the corners of the mouth turned downward.
mouth (v.)
early 14c., "to speak," from mouth (n.). Related: Mouthed; mouthing. Old English had muðettan "to blab." In 17c.-18c. especially "to speak pompously or affectedly." Meaning "form the shape of words with the mouth without uttering them" is by 1953.
