It was for sure 'Trekkie' when I was young. At some point the Trek enthusiasts decided Trekker sounded better. Not surprising - Trekkie was often used in a scornful way by people who weren't fans of Star Trek, as well as the media.
*looks up on wikipedia* Wow, I have a chunk of that wrong! O_o Well, I was young.
https://en.wikipedia.org/wiki/Trekkie
I, myself, have zero issues with fan culture. I'm not into that kind of thing myself, but if people have fun, more power to them! :D And I admit, it does look fun.
My own Trek experience is limited to watching TOS as a kid, and most of the original movies (1-5, I think) at the time of their debuts or on TV. I tried watching the various shows after that, but none of them really grabbed me. I've seen the newest 'remakes', and they didn't have the same impact for me as Wrath of Khan, for example.
But everyone's experience is different, as are tastes! ^_^