http://www.thefreedictionary.com/tenfold

http://www.allwords.com/word-tenfold.html

http://www.elook.org/dictionary/tenfold.html

http://www.lexic.us/definition-of/tenfold

RE:
What does "fold" really mean when used as multiplying?
For a long time I believed that when something said "increase tenfold" or something along those lines, it did NOT mean "increase 10 times"- but rather, 1024 times, or 2 ^10 (how many rectangles you get if you fold paper in half 10 times). Likewise, 5 fold means 32 times….

1. Things don’t really increase when you fold them, and

2. have you ever tried folding something 10 times? It doesn’t work.

I think it really does mean the same thing as multiplication, in that increasing something 10-fold simply means multiplying them by 10.

To me, it also has the sense of ‘aspects’, such as you might describe the Christian deity as being a three-fold god. I feel like this is the ‘original’ meaning. But I haven’t checked the OED.