Concise Bible Dictionary:

1. Fourth son of David by Haggith, born at Hebron (2 Sam. 3:44And the fourth, Adonijah the son of Haggith; and the fifth, Shephatiah the son of Abital; (2 Samuel 3:4)). He was apparently the oldest of David’s sons at the close of David’s life, and may have supposed that he would succeed to the throne; but without consulting his father he said, “I will be king,” and both Joab and Abiathar helped him. David at once proclaimed Solomon as king. Adonijah ran in fear to the horns of the altar, but Solomon promised if he showed himself a worthy man he should not be hurt. He afterward asked to have as wife Abishag, with whom David had shared his bed. According to Herodotus (3.68) this was in eastern countries considered as a pretension to the crown, which agrees with Solomon saying, “Ask for him the kingdom also,” and explains also the advice given by Ahithophel to Absalom, to go in publicly to his father’s wives. Adonijah was at once put to death (1 Kings 2:19-2519Bath-sheba therefore went unto king Solomon, to speak unto him for Adonijah. And the king rose up to meet her, and bowed himself unto her, and sat down on his throne, and caused a seat to be set for the king's mother; and she sat on his right hand. 20Then she said, I desire one small petition of thee; I pray thee, say me not nay. And the king said unto her, Ask on, my mother: for I will not say thee nay. 21And she said, Let Abishag the Shunammite be given to Adonijah thy brother to wife. 22And king Solomon answered and said unto his mother, And why dost thou ask Abishag the Shunammite for Adonijah? ask for him the kingdom also; for he is mine elder brother; even for him, and for Abiathar the priest, and for Joab the son of Zeruiah. 23Then king Solomon sware by the Lord, saying, God do so to me, and more also, if Adonijah have not spoken this word against his own life. 24Now therefore, as the Lord liveth, which hath established me, and set me on the throne of David my father, and who hath made me an house, as he promised, Adonijah shall be put to death this day. 25And king Solomon sent by the hand of Benaiah the son of Jehoiada; and he fell upon him that he died. (1 Kings 2:19‑25)).

Strong’s Dictionary of Hebrew Words:

original (prolonged) dAdoniyahuw {ad-o-nee- yaw'-hoo}; from 113 and 3050; lord (i.e. worshipper) of Jah; Adonijah, the name of three Israelites
KJV Usage:

Jackson’s Dictionary of Scripture Proper Names:

my lord is Jah (Jehovah)

Potts’ Bible Proper Names:

The Lord God; my Lord is Jehovah:―name of three Israelites, 1 Kings 1:5. {Dominus Jehovah}