Someone else probably knows better than me but it's to do with the first ever man who developed the concept of vegetarianism. It was simply called vegetarianism which encompassed the idea that no plants nor animal products were consumed but as they diet evolved and people started cutting out meat but not dairy he wanted another word to define those who didn't consume any animal products at all and the term vegan was born. I can't remember though how he got the word but I think it literally means diet of plants or something like that in another language (you could probably google that bit).<br><br>
ETA: I probably shouldn't have tried to answer this at all! Lol!!
love wikipedia! <img alt="" class="inlineimg" src="http://www.mothering.com/discussions/images/smilies/lol.gif" style="border:0px solid;" title="lol"><br><br>
The word vegan, usually pronounced [ˈviːgən], was originally derived from "vegetarian" in 1944 when Elsie Shrigley and Donald Watson, frustrated that the term "vegetarianism" had come to include the eating of dairy products, founded the UK Vegan Society. They combined the first three and last two letters of vegetarian to form "vegan," which they saw as "the beginning and end of vegetarian."
Here's <a href="http://www.vegansociety.com/html/about_us/history/" target="_blank">a brief history</a> of the Vegan Society, which Watson helped form in 1944.<br><br>
Here's a neat <a href="http://www.foodsforlife.org.uk/people/Donald-Watson-Vegan/Donald-Watson.html" target="_blank">interview</a> with Watson, who died just a couple of years ago, in his 90s.