Who decided to put an X in the frame for a strike and why?

Do we mark an X to cross the thing out, or does the X stand for the Roman numeral 10, as in knocking down 10 pins?

Anyone have any idea?
--------------------
White Dot
It's not the arrow, it's the Indian.
http://bowlingfans.com/league

I think it probably started out meaning 10, but then as the game progressed, and we started having the scores we use today, with the boxes, or whatever they had, they used it to just mark the whole box (like as opposed to shading the whole thing or something like that)
--------------------
16 years and still going strong! 16 years old that is! The names Warrior Princess, Xena..Warrior Princess
And why would I "saw" pins in half, THATS A WASTE OF PINS!