apple (of the eye)

Concise Bible Dictionary:

1. ishoit. Gesenius says this word signifies “little man” and then “the little man of the eye”; that is, “the pupil of the eye in which, as in a mirror, a person sees his own image reflected in miniature.” He says “this pleasing image is found in several languages.” It is the part of the eye specially to be guarded: God preserved His own as the apple of His eye (Deut. 32:1010He found him in a desert land, and in the waste howling wilderness; he led him about, he instructed him, he kept him as the apple of his eye. (Deuteronomy 32:10); Psa. 17:88Keep me as the apple of the eye, hide me under the shadow of thy wings, (Psalm 17:8)). His law should be kept as a precious thing (Prov. 7:22Keep my commandments, and live; and my law as the apple of thine eye. (Proverbs 7:2)).
2. babah, the black or pupil of the eye, or, as others, “the gate of the eye.” To touch God’s people is touching the apple of His eye (Zech. 2:88For thus saith the Lord of hosts; After the glory hath he sent me unto the nations which spoiled you: for he that toucheth you toucheth the apple of his eye. (Zechariah 2:8)).
3. bath, daughter. The sense is, Let not the apple (the daughter) of thine eye cease to shed tears (Lam. 2:1818Their heart cried unto the Lord, O wall of the daughter of Zion, let tears run down like a river day and night: give thyself no rest; let not the apple of thine eye cease. (Lamentations 2:18)). In all places “the apple of the eye” is a beautifully figurative expression for that which must be tenderly cherished as a most choice treasure.

Strong’s Dictionary of Hebrew Words:

feminine active participle of an unused root meaning to hollow out; something hollowed (as a gate), i.e. pupil of the eye
KJV Usage:
apple (of the eye)