Does anyone know the origin of the the word "stofen" and its correct — or at least accepted — spelling? I've seen it spelt "stofen" (which seems to be the most frequent variant), "Stofen", and "Sto-Fen". By stofen I mean the translucent, white, plastic diffusion "cups" that press on to the head of a portable flash.

Although, it seems to me most people use the word "stofen", perhaps it isn't the name most people use. The American company Sto-Fen, offer a "stofen" they market as the Omni-Bounce. And I've seen the word "softy" used and also "diffusion dome" — which, I think is used improperly as the things are rectangular in shape and not domed.

If "stofen" is the canonical form, did the word derived from the name of the Sto-Fen company? And, if so, was it because they invented the "stofen", or simply popularised something that was already in use?