moot point
A debatable question, an issue open to argument; also, an irrelevant question, a matter of no importance. For example, Whether Shakespeare actually wrote the poem remains a moot point among critics, or It's a moot point whether the chicken or the egg came first. This term originated in British law where it described a point for discussion in a moot, or assembly, of law students. By the early 1700s it was being used more loosely in the present sense.