Morty, which is short for Mortimer, is a name I've used most of my life. It started off as a bit fo a silly joke... I am apprenticing as a mortician, and mortuary sciences are something I've been interesting in most of my life... people would call me 'Mort', which essentially means death in french, to my knowledge.
I like the sound of the name Mortimer, so I've just used it.
My family is Doukhobor Russian, and my actual name is strange and quite a mouthful. (It's Aijia.) Though that name is uni-sex, I still rather dislike it, and it sounds too feminine to me.
Some people still call me by that name, though, but mostly close friends and family.