John Gill 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)

And forty one years reigned he in Jerusalem
Being a good king, had the blessing of a long reign, and reached, and even exceeded, the years of the reigns of David and Solomon:

and his mother's name was Maachah, the daughter of Abishalom ;
that is the name of his grandmother, see (1 Kings 15:2) she is called his mother, not because she brought him forth, but because she brought him up; and this is observed to his commendation, that though he was educated by an idolatrous woman, yet was not corrupted by her as his father was.