vegetate (v.) c. 1600, "to grow as plants do," perhaps a back-formation from vegetation, or from Latin vegetatus, past participle of vegetare "to enliven, to animate" (see vegetable (adj.)). Sense of "to lead a dull, empty, or stagnant life" is from 1740. Related: Vegetated; vegetating.
veg since 1898 as an abbreviation of vegetarian; 1918 of vegetable. As a verb, colloquially short for vegetate, by 1985 (usually with out).