Was originally going to ask this in c/transenby_liberation, but that comm's sidebar says to put these questions here.

I know generally what truscum are -- people who gatekeep transgenderness using arbitrary medical or psychological criteria -- I'm asking about the origin of the word itself. "Scum" is pretty self-explanatory, but what about "tru?" Is it because they try to tell people they're not "true trans people"?

Feel free to expand on the definition too of course.