Is there a well-known name for this?

From time to time I and colleagues find ourselves extending some function in C in a way that requires extra arguments. Often this happens in a context where it's impractical to change all the callers (for instance, because some of them are in customer code) so the extended version of the function gets a new name and the original name just calls that with some default value of the new arguments.

For instance I might go from this:

int refine_glorp(glorp *g) {
  /* refinement */
}

…to this:

int refine_glorp(glorp *g) {
  return refine_glorp_ex(g, 0);
}

int refine_glorp_ex(glorp *g, int arg) {
  /* extended refinement, based on arg */
}

Is there a well-known name for this transformation?

A colleague who did this a week or so ago started out with 'decapitation' but changed his mind to 'recapitation' on the grounds that he was really adding a second head to the function rather than removing one. But neither of us knew if there was already a name for this.