"Conlang" is short for "constructed language." Look it up; you'll find a large amount of weirdos, like me, who find creating a language to be an interesting thing.
Tethrinoth is mine. I've already got the phonology mostly worked out and I already have a writing system. The lexicon has about 30 words thus far.
"Why," you ask? I've studied French, Spanish, Japanese, German, and Russian. I am fascinated by language yet I have never successfully come to fluency in any one (other than English). Years of language study gone to waste, it seems, because I can't focus on just one. Years of massive brain overload and I give up . . . kinda.
Enter constructed languages.
I've always fantasized about speaking my own private language. Many years ago, my friend and I even made up our own written language. It was called Seeksorchay. It didn't last very long as our interests at the time were taken up more by playing punk music. The thought has been with me ever since to create an entirely new language. On a whim one day I googled "make own language" and found the language construction kit at zompist.com. The rest is history.