It doesn't mean anything, it's just a silly contortion of Mirjami.
It just sounds stupid.
"Mirde" also feels kind of stupid to me nowadays, I mean, no one ever uses it of me. I don't know why I chose it as my nick here.
That's interesting, Stephen. My specialty at uni is onomastics, which is study of names, and I know a guy who did his master's thesis on internet nicks. He discovered that the most common way to form a nick is exactly how you described: someone's already got your name so you add a number (often it's the year of birth, but sometimes just random) and maybe a _.
So stephen_09 is the prototype of internet nicks.
