Apple Of My Eye – Monday’s Confused Word Search Puzzle

So, what exactly does “apple of my eye” mean?
Does it mean you have an apple growing out of your eye?
Could it mean you have your eye on an apple?
I think it means you are supposed to go look it up on the Internet and get 2,387,914 results so you just go with the first one and pretend it’s right.
It would take a long time to check the other 2,387,913 results.