Mine came from 2 sources relevant to my life at the time back in the early 90's. One was from my friends punk band Old Nick that had a song called "Gillette". The lyrics go...
"This guy they call Gillette, was out back siphoning gas.
So I went out in the alley, and kicked his goddamned ass.
He's got a nice complexion, his head's stuck in a vial.
To bring those tears to his face, really made me smile.
So why's he gotta go, and do that crazy stuff?
I just don't fucking get it, this guy is credo tough.
I'm gonna kick his ass, repeatedly I say.
Until this little fucker, decides to go away."
That song was always stuck in my head because it was not only an actual true story, but a fucking awesome tune.
The second source is during this time I was working for a major lock and door hardware company. There is something called "The Locksmiths Credo" that we all had to learn. Something about taking people's sense of security to heart etc.
So I just liked the sound of credo and that it basically means to take an oath of sorts, and changed it to "Creedo" to sort of make it my own.