It's "KERNEL", not "KERNAL".
The kernel is generally defined as the core of an operating system - in fact, the word "kernel" relates to the old german word "kerne", which means "seed" or "core".
The KERNAL was the core operating system of some early 8-bit Commodore computers, from the PET computer of 1977 up until the C64/C128, as well as the VIC-20 and other models. It handled low level system calls under the BASIC interpreter. The KERNAL IS a kernel. A kernel, however, is NOT a KERNAL.
An old theory in the C64 community goes that some unknown programmer at Commodore misspelled the word "kernel" and it stuck; another theory is that the word "KERNAL" is an acronym for "Keyboard Entry Read, Network And Link" (I'm leaning toward the first explanation).
I don't mean to whine, I just figured some people might appreciate the info.