tummy n.

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 (Old English maga glosses stomachus).

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.

a general Germanic word for "leather bag, pouch, pod" that in English has evolved to mean a part of the body; Middle English beli, from from Old English belg, bylig (West Saxon), bælg (Anglian) "leather bag, purse, pouch, pod, husk, bellows," from Proto-Germanic *balgiz "bag" (source also of Old Norse belgr "bag, bellows," bylgja "billow," Gothic balgs "wine-skin"), from PIE *bhelgh- "to swell," extended form of root *bhel- (2) "to blow, swell."

By c. 1200 it was being used for "the stomach," especially as a symbol of gluttony, and by late 14c. to mean "abdomen of a human or animal, front part of the body between the breast and the groin or the diaphragm and the pelvis."

The Old English word for "belly, stomach" was buc (cognate with German Bauch, Dutch buik, Old Frisian buk, from West Germanic *būkaz, a word indicative of swelling, with no known connections).

The plural of Old English belg emerged in Middle English as a separate word, bellows. The meaning "bulging part or convex surface of anything" is 1590s. The West Germanic root had a figurative or extended sense of "anger, arrogance" (as in Old English bolgenmod "enraged;" belgan (v.) "to become angry"), probably from the notion of "swelling."

Indo-European languages commonly use the same word for both the external belly and the internal (stomach, womb, etc.), but the distinction of external and internal is somewhat present in English belly/stomach; Greek gastr- (see gastric) in classical language denoted the paunch or belly, while modern science uses it only in reference to the stomach as an organ.

As a personal name from 12c. Belly-naked in Middle English was "stripped to the belly, completely naked." Fastidious avoidance of belly in speech and writing (compensated for by stretching the senses of imported stomach and abdomen, baby-talk tummy and misappropriated midriff) began late 18c. and the word was banished from Bibles in many early 19c. editions.