Interestingly, the Ur-Lisp (Lisp 1.5) actually had both. There were two ways to define a function. There was one form, LABEL (the ancestor of CL's LABELS), which bound a function like a variable, and another form, DEFINE, that put the function on the symbol's property list. APPLY would check the property list first, then look for a variable binding.

From the Lisp 1.5 manual (1962):

"In actual practice, LABEL is seldom used. It is usually more convenient to attach the name to the definition in a uniform manner... The fact that most functions are constants defined by the programmer, and not variables that are modified by the program, is not due to any weakness of the system. On the contrary, it indicates a richness of the system which we do not know how to exploit very well."