Asa degraded Maachah from the rank and state of queen-mother.
The word translated “idol” both here and in the parallel passage (marginal reference), does not occur elsewhere in Scripture. It is derived from a root signifying “fear” or “trembling,” and may perhaps best be understood as “a fright, a horror.” Such a name would seem best to apply to a grotesque and hideous image like the Phthah of the Egyptians. She made it to serve in lieu of the ordinary “grove” - asherah, or idolatrous emblem of Astarte (Exodus 34:13 note). Asa cut it down, for like the usual “asherah,” Maachah’s “horror” was fixed in the ground.
And burnt it at the brook Kidron - Similarly Josiah, when he removed Manasseh’s “grove” - asherah - from the house of the Lord, brought it out to the brook Kidron, and burned it there. The object probably was to prevent the pollution of the holy city by even the ashes from the burning.