I read that the company was spelled that way up until world war 2 era when the nazi's were being shitheads. So as an american company, rickenbacker americanized their name by adding the k and removing the h.
My understanding is that is was just a spelling error on early rics, but the nazi thing makes sense. My last name went through a couple of different pronunciations in order to make it a little more...unethnic. robrtnickerson is not my real name. I travel the internets under a thinly veiled cloak of anonimity.