The apple of my eye

I was goofing off and looking at my roommate through a pretend telescope, when she suddenly announced, "I can see the apple of your eye!"

I froze. Had she read my mind? How did she know what I was thinking about?

"What do you mean?" I asked.

"I can see this part of your eye," she said, pointing to her own eye.

"Ummmm, the apple of your eye is the thing you cherish most," I said, confused.

"But this expression comes from the name of this part of your eye."

"What part? The eyeball?"

"No, here. The center."

"The iris?"

"No, the white."

"That's called the 'sclera,'" I said, positive that we hadn't covered "apple" in biology class.

"It is just a name for the middle of the eye," she insisted. "We have it in Russian too."

"Okay, I just didn't understand because even if that is the origin, we don't actually use it that way. We use it to describe something that is the center of your life."

I went to look it up on Google. She was right.

According to this site, the phrase originally referred to "the central aperture of the eye." Sir Walter Scott used the phrase figuratively in "Old Mortality," 1816: "Poor Richard was to me as an eldest son, the apple of my eye."

And it is also, of course, found in the Bible.

In Deuteronomy, the Lord cares for His inheritance:

In a desert land he found him, in a barren and howling waste. He shielded him and cared for him; he guarded him as the apple of his eye, (32:10)

Another example is Zechariah 2:8.

For this is what the LORD Almighty says: "After he has honored me and has sent me against the nations that have plundered you—for whoever touches you touches the apple of his eye-