The English word "darling" originated from an old Anglo-Saxon word, deorling, which meant beloved. The English word dear has the same origin i.e. dear and darling are actually the same word.
The King James Version uses "darling" only twice, to translate the Hebrew word, pronounced yaw-kheed, that itself only occurs twice in the Holy Scriptures. The Hebrew word actually has a much wider meaning than the "darling" that is used to translate it; it literally means united, but is also used to refer to someone who is beloved, but moreover, an irreplaceable life. Surprisingly, both occurrences of the word in the Scriptures were spoken by King David - about himself.
"22:20 Deliver my soul from the sword; my darling from the power of the dog." (Psalm 22:20 KJV)
"35:17 Lord, how long wilt thou look on? rescue my soul from their destructions, my darling from the lions." (Psalm 35:17 KJV)
Consider how the RSV translates the same verses with "my life" instead of "my darling":
"22:20 Deliver my soul from the sword, my life from the power of the dog!" (Psalm 22:20 RSV)
"35:17 How long, O LORD, wilt thou look on? Rescue me from their ravages, my life from the lions!" (Psalm 35:17 RSV)
"My God, my God, why hast thou forsaken me?"
David wasn't being an "I'm all the love that I need" narcissist when he referred to himself as "my darling" - because in the original words, that isn't what he said. He was referring to a righteous person being precious in God's sight. That was the whole point of David's prayers, which in fact are what those two Psalms are - the pleas of a righteous man to be delivered from those who were attacking him because he obeyed the LORD.
"35:17 Lord, how long wilt thou look on? rescue my soul from their destructions, my darling from the lions. 35:18 I will give thee thanks in the great congregation: I will praise thee among much people.
35:19 Let not them that are mine enemies wrongfully rejoice over me: neither let them wink with the eye that hate me without a cause. 35:20 For they speak not peace: but they devise deceitful matters against them that are quiet in the land. 35:21 Yea, they opened their mouth wide against me, and said, Aha, aha, our eye hath seen it.
35:22 This thou hast seen, O LORD: keep not silence: O LORD, be not far from me.
35:23 Stir up thyself, and awake to my judgment, even unto my cause, my God and my Lord.
35:24 Judge me, O LORD my God, according to thy righteousness; and let them not rejoice over me. 35:25 Let them not say in their hearts, Ah, so would we have it: let them not say, We have swallowed him up.
35:26 Let them be ashamed and brought to confusion together that rejoice at mine hurt: let them be clothed with shame and dishonour that magnify themselves against me. 35:27 Let them shout for joy, and be glad, that favour my righteous cause: yea, let them say continually, Let the LORD be magnified, which hath pleasure in the prosperity of his servant. 35:28 And my tongue shall speak of thy righteousness and of thy praise all the day long." (Psalm 35:17-28 KJV)
David's use of the term in Psalm 22 has an even greater significance; his "My God, my God, why hast thou forsaken me?" in verse 1 were the very words that the Messiah later used when His Sacrifice was fulfilled (see the Fact Finder question below). The "they pierced my hands and my feet" in verse 16 was what happened to Christ, not to David, when David prophesied it in this Psalm.
"22:1 To the chief Musician upon Aijeleth Shahar, A Psalm of David. My God, my God, why hast thou forsaken me? why art thou so far from helping me, and from the words of my roaring?
22:2 O my God, I cry in the daytime, but thou hearest not; and in the night season, and am not silent. 22:3 But thou art holy, O thou that inhabitest the praises of Israel.
22:4 Our fathers trusted in thee: they trusted, and thou didst deliver them.
22:5 They cried unto thee, and were delivered: they trusted in thee, and were not confounded.
22:6 But I am a worm, and no man; a reproach of men, and despised of the people.
22:7 All they that see me laugh me to scorn: they shoot out the lip, they shake the head, saying, 22:8 He trusted on the LORD that he would deliver him: let him deliver him, seeing he delighted in him.
22:9 But thou art he that took me out of the womb: thou didst make me hope when I was upon my mother's breasts. 22:10 I was cast upon thee from the womb: thou art my God from my mother's belly. 22:11 Be not far from me; for trouble is near; for there is none to help.
22:12 Many bulls have compassed me: strong bulls of Bashan have beset me round. 22:13 They gaped upon me with their mouths, as a ravening and a roaring lion. 22:14 I am poured out like water, and all my bones are out of joint: my heart is like wax; it is melted in the midst of my bowels. 22:15 My strength is dried up like a potsherd; and my tongue cleaveth to my jaws; and thou hast brought me into the dust of death. 22:16 For dogs have compassed me: the assembly of the wicked have enclosed me: they pierced my hands and my feet. 22:17 I may tell all my bones: they look and stare upon me. 22:18 They part my garments among them, and cast lots upon my vesture. 22:19 But be not thou far from me, O LORD: O my strength, haste thee to help me. 22:20 Deliver my soul from the sword; my darling from the power of the dog." (Psalm 22:1-20 KJV)
Fact Finder: Why did God turn away from the Messiah at the moment that all of humanity's sins were put upon Him?
See Eloi, Eloi, Lama Sabachthani?