When your little growing up at home (in america and in my case) parents refer to it as bathroom, why di you say well because it is the room of the hoise that contains the bath! So just being so used yo calling the room with the toilet a bathroom and not thinking twice about itits definetely a funny term like when at school or a restraunt there is no bath (most likely) in the room! So yes if u come from a diffrent country public places do post restroom signs on the "bathroom" doors