Originally Posted by ixtab
It stems from the time when the Kindle 4 and Kindle Touch were released, and *both* of them were referred to as "K4" ("Touch" and "Non-Touch) - even if that's obviously wrong, because the Touch is a K5.
It's only "obviously wrong" if you're referring to firmware versions. When people started using the term "K4", they simply mean "the 4th generation Kindle". The fact that it was firmware version 4 really had nothing to do with it.