I have two questions:

(1) Is a postulate the same thing as an axiom? This [answer](https://math.stackexchange.com/questions/7717/difference-between-axioms-theorems-postulates-corollaries-and-hypotheses) seems to suggest the answer is yes. I've always thought the two were the same but the question below suggests a difference.

(2) If the answer to (1) is yes, then why is [Bertrand's Postulate](https://en.wikipedia.org/wiki/Bertrand%27s_postulate) so named? It is a theorem, one can prove it. Was it taken as an axiom at one point or is this just a sort of "abuse of terminology?"

I guess, if said naming is indeed an abuse of terminology, my opinion is that this abuse is not totally benign. When I first heard of Bertrand's Postulate, it was mentioned in a proof in the following manner: "We see that Statement X follows immediately from Bertrand's Postulate." Not familiar with the theorem, I assumed this was another name for some famous axiom, which was confusing to me since I knew of no axiom which readily implied the result. Upon looking up Bertrand's Postulate, my misconception was cleared up but I was left wondering why they called it a postulate.