Mine is a shortened version of a nickname I gained in high school.
It was back in the 1980s, in the era before widespread access to the Internet, when computer geeks and punk kids (I fell into both groups

) used their modems to call up "bulletin board systems" to leave messages to each other like we do on here. I was trying to come up with a name somewhat like that of Johnny Rotten from Sex Pistols and P.I.L., given that my first name is John. Johnny Morbid seemed to fit since I was kind of a goth.
It change to Johnny Morbyd in '88 when I got personalized "Morbyd" license plates for my first car ("Morbid" was taken

)
It got shortened to just Morbyd in the early '90s when I got my first Internet account.