Apple; Apple Tree

Boyd’s Bible Dictionary:

(bursting forth, in Hebrew). The fruit is alluded to (Prov. 25:11¹¹A word fitly spoken is like apples of gold in pictures of silver. (Proverbs 25:11); Song of Sol. 2:5; 7:8⁵Stay me with flagons, comfort me with apples: for I am sick of love. (Song of Solomon 2:5)
⁸I said, I will go up to the palm tree, I will take hold of the boughs thereof: now also thy breasts shall be as clusters of the vine, and the smell of thy nose like apples; (Song of Solomon 7:8)). Tree mentioned (Song of Sol. 2:3; 8:5³As the apple tree among the trees of the wood, so is my beloved among the sons. I sat down under his shadow with great delight, and his fruit was sweet to my taste. (Song of Solomon 2:3)
⁵Who is this that cometh up from the wilderness, leaning upon her beloved? I raised thee up under the apple tree: there thy mother brought thee forth: there she brought thee forth that bare thee. (Song of Solomon 8:5); Joel 1:12¹²The vine is dried up, and the fig tree languisheth; the pomegranate tree, the palm tree also, and the apple tree, even all the trees of the field, are withered: because joy is withered away from the sons of men. (Joel 1:12)). For figurative use see Prov. 7:2²Keep my commandments, and live; and my law as the apple of thine eye. (Proverbs 7:2); 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); Psa. 17:8⁸Keep me as the apple of the eye, hide me under the shadow of thy wings, (Psalm 17:8); 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).

Concise Bible Dictionary:

This is generally supposed to refer to the citron but apples grow in Palestine, and the Arabic name for the apple (tuffuh) differs little from the Hebrew word, tappuach. Others believe the quince is alluded to, which is fragrant and of a golden color. (Song of Sol. 2:3,5³As the apple tree among the trees of the wood, so is my beloved among the sons. I sat down under his shadow with great delight, and his fruit was sweet to my taste. (Song of Solomon 2:3)
⁵Stay me with flagons, comfort me with apples: for I am sick of love. (Song of Solomon 2:5); Song of Sol. 7:8⁸I said, I will go up to the palm tree, I will take hold of the boughs thereof: now also thy breasts shall be as clusters of the vine, and the smell of thy nose like apples; (Song of Solomon 7:8); Song of Sol. 8:5: Joel 1:12¹²The vine is dried up, and the fig tree languisheth; the pomegranate tree, the palm tree also, and the apple tree, even all the trees of the field, are withered: because joy is withered away from the sons of men. (Joel 1:12)). In Prov. 25:11¹¹A word fitly spoken is like apples of gold in pictures of silver. (Proverbs 25:11) “a word fitly spoken” is like some elegant device, as “apples of gold in pictures [or baskets] of silver.”