Albert Barnes Commentary 1 Kings 15:10

"And forty and one years reigned he in Jerusalem: and his mother`s name was Maacah the daughter of Abishalom." — 1 Kings 15:10 (ASV)

Mother’s name - Rather, “grandmother’s.” The Jews call any male ancestor, however remote, a father, and any female ancestor a mother (Compare to 1 Kings 15:2; Genesis 3:20). This Maachah was the favorite wife of Rehoboam (2 Chronicles 11:21) and the mother of Abijam. The way in which she is mentioned here strongly favors the idea that the position of queen-mother was a definite one at the court and could only be held by one person at a time.