So, an involutory function is a function that is its own inverse. In other words, a recursive call to this function would return the original input:
$$f(f(x)) \equiv x$$
Suppose we had a function with a similar property, but with more than additional recursions required:
e.g. $$f(f(f(x))) \equiv x$$
Is there any existing term to describe this (for the specific example given above, or generalized to n-recursions)? If not, how would you go about making up a new term to describe it?
This is sometimes called a functional ($n$-th) root of the identity.
See here.