Seems one etymology of the octothorp has to do with the layout of towns where the eight plots surrounding the common area were populated.

“Otherwise known as the numeral sign. It has also been used as a symbol for the pound avoirdupois, but this usage is now archaic. In cartography, it is also a symbol for village: eight fields around a central square, and this is the source of its name. Octothorp means eight fields.”

http://www.brodynewmedia.com/Octothorp.html