Looking at the word vegan, it's surprisingly obvious to see its origin, but hard to notice at first. It's a clipping of vegetarian, used by a radical new society in the 1940s which wanted to distinguish itself from its inhumane predecessors. This word comes from the word vegetable, with the addition of the suffix denoting a person, -an. Originally, around the time when Linnaeus used it, a vegetable was any type of plant, but later it grew more specific. Since veggies are living and humankind knew it, the word traces to French vegetable, or "living" (which makes the word's usage as "brain-dead person" all the more ironic). This is from Latin vegetabilis, which meant "able to live and grow", from vegere, "to be alive or active". This is most likely from the reconstructed Proto-Indo-European word weg, which meant "strong or lively", proving that your mother was right about the connection between eating your greens and becoming stronger.
Adam Aleksic, a rising sophomore studying linguistics and government at Harvard University, has been described as the internet's sixth most famous etymologist. He also has disturbing interests in politics, vexillology, geography, board games, conlanging, and law.