Is 'gender' based on how the majority act, or an arbitrary definition?
Good question!
I've always thought that what came first was patriarchy and oppression, based on women's weaker physical structure and the fact that pregnancy and childbirth, and everything in between, would restrict our "freedoms" and the time that we had to improve on our personal situations, in order to remove barriers.
With patriarchy and oppression embedded, societies were arranged around the Man, and women therefore "became feminine" (meaning oppressed, restricted, and powerless, both physically and societally).
So that became "feminine gender." And all the accoutrements of "feminine gender" were perpetuated and seen as "normal" for women, within society. These became the stereotypes.
Of course, different societies had, and have, different expectations of "feminine gender" ( and, by extension, women). If there have been societies wherein women were expected to be strong, money-making, bringing home the bacon, do all the fighting, etc., then "feminine" in that society would have meant those things.
In most Western, patriarchal societies, however, "feminine " came to mean submissive, obedient, weak, dependent, etc., because that's what women were expected, and allowed, to be.
Does that make sense? Or am I reaching?