That sounds right. And hangon points out that the common meaning for "behavior" is "expected behavior". So I'm really saying that the expectation is undefined.

That does seem to be how languages evolve. But when the referent is the part that got left out or left behind, it can be very annoying to more cultured ears. Like a home-improvement show says "to poly the bookcase". Er, the verb you wanted is varnish. But was "varnish" itself a noun that got turned into a verb? Apparently the word can be traced all the way back to the name of the Greek city of Κυρηναϊκή. Go figure.