Old English etan (class V strong verb; past tense æt, past participle eten) "to consume food, devour, consume," from Proto-Germanic *etan (source also of Old Frisian ita, Old Saxon etan, Middle Dutch eten, Dutch eten, Old High German ezzan, German essen, Old Norse eta, Gothic itan), from PIE root *ed- "to eat."
Transferred sense of "corrode, wear away, consume, waste" is from 1550s. Meaning "to preoccupy, engross" (as in what's eating you?) first recorded 1893. Slang sexual sense of "do cunnilingus on" is first recorded 1927. The slang phrase eat one's words "retract, take back what one has uttered" is from 1570s; to eat one's heart out is from 1590s; for eat one's hat, see hat. Eat-in (adj.) in reference to kitchens is from 1955. To eat out "dine away from home" is from 1930.
Old English etere "one who eats," especially a servant or retainer, agent noun from eat (v.)). From 17c. in compounds with various objects or substances eaten.
edible, fit to be used for food," "1620s, from Latin esculentus "good to eat, eatable, fit to eat," from esca "food," from PIE *eds-qa- (source also of Lithuanian ėska "appetite"), from root *ed- "to eat." As a noun from 1620s, "food, especially vegetables."