late 13c., "sound made by the human mouth," from Old French voiz "voice, speech; word, saying, rumor, report" (Modern French voix), from Latin vocem (nominative vox) "voice, sound, utterance, cry, call, speech, sentence, language, word" (source also of Italian voce, Spanish voz), related to vocare "to call" (from PIE root *wekw- "to speak").
Replaced Old English stefn "voice," from Proto-Germanic *stemno, from PIE *stomen- (see stoma). Meaning "ability in a singer" is first attested c. 1600. Meaning "expression of feeling, etc." (in reference to groups of people, etc., such as Voice of America) is recorded from late 14c. Meaning "invisible spirit or force that directs or suggests," (especially in the context of insanity, as in hear voices in (one's) head, is from 1911.
late 14c. variant of earlier stomake (early 14c.), "internal pouch into which food is digested," from Old French stomaque, estomac "stomach," from Latin stomachus "throat, gullet; stomach," also "taste, inclination, liking; distaste, dislike;" also "pride, indignation," which were thought to have their origin in that organ (source also of Spanish estómago, Italian stomaco), from Greek stomachos "throat, gullet, esophagus," literally "mouth, opening," from stoma "mouth" (see stoma).
Applied anciently to the openings of various internal organs, especially that of the stomach, then by the later Greek physicians to the stomach itself. The native word is maw. Some 16c. anatomists tried to correct the sense back to "esophagus" and introduce ventricle for what we call the stomach. Meaning "belly, midriff, part of the body that contains the stomach" is from late 14c.
In Middle English also stomack,stomac, stommak,stomoke; the spelling of the ending of the word was conformed to Latin regularly from 16c., but the pronunciation remains as in Middle English. Related: stomachial (1580s); stomachical (c. 1600); stomachic (1650s). Pugilistic stomacher "punch in the stomach" is from 1814; from mid-15c. as "vest or other garment which covers the belly." The Latin figurative senses also were in Middle English (such as "relish, inclination, desire," mid-15c.) or early Modern English. Also sometimes regarded in Middle Ages as the seat of sexual desire.