My understanding of the 16" framing system is that the size of a brick was established by royal decree.(A roman "brick" took 2 men to handle, the English realized that a better way was to hold a smaller brick in one hand and a trowel in the other) Later it was decreed that a fireplace would be a minimum of 2 bricks wide. This made firewood typically 16" long. Owner builders having moved into their home's shell would while away the winter splitting and applying lath, the easiest source was the woodpile and so they studded accordingly. This came from David Lyle's "The Book of Masonry Stoves". It's the only place I've seen that story.