There used to be an electricain who always had notes or quick look-ups to the most terms, formulas, tables, NEC ....etc. so he kept a notepad/notbook with all this info in it. However, it was never organized and it was all handwritten and all his co-workers were refering to his notes. so he decided to use his notbook/notpad and make a fortune out of it.
And since it was never organized he called his yellow book UGLY'S.
I beleive that's where the name came from.