A lot vs. Alot: 9 Grammatical Pitfalls
1839, irregular formation from vegetable (n.) + -arian, as in agrarian, etc. "The general use of the word appears to have been largely due to the formation of the Vegetarian Society in Ramsgate in 1847" [OED].
vegetarian veg·e·tar·i·an (věj'ĭ-târ'ē-ən)n. One who practices vegetarianism. adj.
Of or relating to vegetarianism or vegetarians.
Consisting primarily or wholly of vegetables and vegetable products.