I agree with Rani that screen names can become sort of a "persona". Most of the time I use my screen name like a name but will always sign off a message with my real name, Geof!! It starts to become like a different person after awhile, and I commonly refer to my wife on here as "Mrs. C"!!!
Cosgig is not a name by any means, just the initials of my band that I've had since 1989, "Company of Strangers", and my kids initials... Genelle and Ian Galliher. I've used it for years everywhere else, why not here too!! Geof