Uhh kind of a bad way of phrasing it IMO, "martial art" in the historical context just means a practice or idea or manner of conducting fighting. Therefore archery was a martial art, and if you applied it today you could loosely say that using an Ak74 is a martial art.

By your examples you mean unarmed fighting, or at least grappling fighting, and well there is no one Buddha or Jesus of it. People need/want to defend/hurt others/themselves and that is a need that has existed from 2014 and when Julius C. lived.

So it's sort of an amalgamation between culture naming stuff that's similar (kung fu is a chinese word, karate isn't) and individuals and society slowly shaping perceived differences.