What does 'ap' stand for in C examples?

Question

For example, in the reference:

type va_arg (va_list ap, type)

Does ap stand for argument pointer? Something else?

Answer 1

That's actually an easy question to answer.

ap stands for argument pointer.

From The C Programming Language, Second Edition, Brian W. Kernighan and Dennis M. Ritchie:

7.3 Variable-length Argument Lists

[...] The type va_list is used to declare a variable that will refer to each argument in turn; in minprintf, this variable is called ap, for "argument pointer"