Python is the language I know the most, and strangely I still don\'t know why I\'m typing \"self\" and not \"this\" like in Java or PHP.
I know that Python is older
I think that since it's explicitly declared it makes more sense seeing an actual argument called "self" rather than "this". From the grammatical point of view at least, "self" is not as context dependent as "this".
I don't know if I made myself clear enough, but anyway this is just a subjective appreciation.