apple of

the apple of (one's) eye

A cherished or favored person. This phrase is thought to be Biblical in origin. My nephew is just the apple of my eye. He has five kids, but his only daughter is clearly the apple of his eye.
See also: apple, eye, of

apple of (someone's eye)

Fig. someone's favorite person or thing; a boyfriend or a girlfriend. Tom is the apple of Mary's eye. She thinks he's the greatest. John's new car is the apple of his eye.
See also: apple, of
References in classic literature ?
And he won't let a soul but a Dalmatian pick a single apple of all those apples.
Two Poets were quarrelling for the Apple of Discord and the Bone of Contention, for they were very hungry.
"The fatal apple of Eden couldn't have had a rarer flavor," commented Anne.
My most favorite apple of all time has a snow-white flesh and is supercrisp and juicy.