Not strictly IT related
I picked up SFB (Shit For Brains) from The Mother in Law. She found it written in the comments section of case notes when she worked at a youth detention centre. Her first guess was State Funding Board...
She also used FLK (Funny Looking Kid) when she worked with what used to be called retarded children. It means "there's something wrong with the child but we don't have a diagnosis and I can't put my finger on it"