Um...what?

As I mentioned in a previous post, there were a couple phrases, idioms, euphemisms, whatever they're called whose origins were shrouded in mystery. At least, to me. And since the reality found here is of my own creation, they are officially shrouded in mystery.

The first was 'dead ringer'. Now, to give myself a little credit, I am familiar with other such phrases (I'm going with phrases okay? You don't like it, write a letter to somebody.) that institute similar words. For instance. 'Saved by the bell' comes from the practice of attaching a bell to the gravestone with a string trailing down in to the buried casket. The point of which was to prevent anyone from being buried alive.

Another olde tyme phrase with similar word usage is 'Send in the ringer'. Of course as we all know this one is in reference to a competition of some kind in which a participant is entered under false pretenses or presented in such a way to misrepresent their abilities. Neither of which has anything to do with somebody looking exactly like somebody else.

The other one was 'apple of my eye'. I got nothin' on that one. The best I can come up with is the 'apple a day keeps the doctor away', which makes no sense whatsoever. Or maybe people used to somehow mistake small apples for eyeballs? Any ideas? Or do you have any such phrases whose origins are unknown?