The Wikipedia article about the # sign has its own shaky theories about the origin of the symbol, but I'm finding that there's a striking resemblance between the shape of a German Current capital "N" and the #, a scribble that has evolved to mean "Number." Tell me with a straight face that you don't also notice the resemblance here.
And is it no mistake that N and # stand for "Number?" I think not. Too many striking similarities, in my opinion.