Thanks for all the replies - Bert, the reason it got a 3 star rating was because it lead me to the answer. I now know the origin is biblical and thats what I was looking for - being as un-biblical as a person can be, I wouldn't have a clue about the chapters and names etc. Although I understand this is still part of the answer, the main thing I wanted was how it came about and Quizmonster's answer was sufficient. :)