I have never heard of the Vegan Society before; I suspect most people you interact with haven't either, even including those who are vegan due to ethical concer

I have never heard of the Vegan Society before; I suspect most people you interact with haven't either, even including those who are vegan due to ethical concerns. Could you explain why a random person should see this particular organization as having authority to define what the term means versus, say, their dictionary or Wikipedia? e.g., did this organization perhaps invent the word "vegan" originally? (I don't know the etymology.)