C. F. Keil and Franz Delitzsch on 2 Chronicles 11:20

2Ch 11:20

Maachah the daughter, i.e., the granddaughter, of Absalom; for she cannot have been Absalom’s daughter, because Absalom, according to 2Sa 14:27, had only one daughter, Tamar by name, who must have been fifty years old at Solomon’s death. According to 2Sa 18:18, Absalom left no son; Maachah therefore can only be a daughter of Tamar, who, according to 2Ch 13:2, was married to Uriel of Gibeah: see on 1Ki 15:2. Abijah, the oldest son of Maachah, whom his father nominated his successor (2Ch 11:22 and 2Ch 12:16), is called in the book of Kings constantly Abijam, the original form of the name, which was afterwards weakened into Abijah.