Where does the phrase 'to have your cake and eat it' come from ? Also if you have your cake, what else would you do but eat it....seems a bit silly really ?
The correct phrase is that "you can't eat your cake and have it too". It goes back a long way, to at least the 16th century, but I don't think there's any particular derivation - it's simply a saying. Yes, it does sound a little odd nowadays, as we use the verb "to have" to mean "to eat", but it makes sense if you think of it as "you can't eat your cake and keep it too".
The phrase "eat your cake and have it too" is not simply a saying, it's Shakespeare. The saying "have your cake and eat it too" is a long-standing misquote.