As I recall...
...people started to refer to themselves as Trekkies. Then some outsiders started to refer to them that way, in the third person. Then some of them took offense and decided they liked Trekker better.
cf: negro, teabagger, scifi (Harlan Ellison once had a beef with it. Thought that SF should stand for speculative fiction.) etc.
From the way you posed the question I gather you have some other story. Can't wait to hear it.