The term "vegetarian" has been in use since around 1839 to refer to what was previously described as a vegetable regimen or diet. Its origin is an irregular compound of vegetable and the suffix -arian (in the sense of "supporter, believer" as in humanitarian). The earliest known written use is attributed to actress, writer and abolitionist Fanny Kemble, in her Journal of a Residence on a Georgian plantation in 1838–1839.
Vegetarianism can be traced to Indus Valley Civilization in 3300–1300 BCE in the Indian subcontinent, particularly in northern and western ancient India. Early vegetarians included Indian philosophers such as Mahavira, Acharya Kundakunda, and the Tamil poet Valluvar; the Indian emperors Chandragupta Maurya and Ashoka; Greek philosophers such as Empedocles, Theophrastus, Plutarch, Plotinus, and Porphyry; and the Roman poet Ovid and the playwright Seneca the Younger. The Greek sage Pythagoras may have advocated an early form of strict vegetarianism, but his life is so obscure that it is disputed whether he ever advocated any form of vegetarianism at all. He almost certainly prohibited his followers from eating beans and from wearing woolen garments. Eudoxus of Cnidus, a student of Archytas and Plato, writes that "Pythagoras was distinguished by such purity and so avoided killing and killers that he not only abstained from animal foods, but even kept his distance from cooks and hunters". One of the earliest known vegans was the Arab poet al-Maʿarri (c. 973 – c. 1057). Their arguments were based on health, the transmigration of souls, animal welfare, and the view—espoused by Porphyry in De Abstinentia ab Esu Animalium ("On Abstinence from Animal Food", c. 268 – c. 270)—that if humans deserve justice, then so do animals.
Vegetarianism established itself as a significant movement in 19th-century Britain and the United States. A minority of vegetarians avoided animal food entirely. In 1813, the poet Percy Bysshe Shelley published A Vindication of Natural Diet, advocating "abstinence from animal food and spirituous liquors", and in 1815, William Lambe, a London physician, stated that his "water and vegetable diet" could cure anything from tuberculosis to acne. Lambe called animal food a "habitual irritation", and argued that "milk eating and flesh-eating are but branches of a common system and they must stand or fall together". Sylvester Graham's meatless Graham diet—mostly fruit, vegetables, water, and bread made at home with stoneground flour—became popular as a health remedy in the 1830s in the United States. Several vegan communities were established around this time. In Massachusetts, Amos Bronson Alcott, father of the novelist Louisa May Alcott, opened the Temple School in 1834 and Fruitlands in 1844, and in England, James Pierrepont Greaves founded the Concordium, a vegan community at Alcott House on Ham Common, in 1838.