Charles Ellicott Commentary Jeremiah 9:14

"but have walked after the stubbornness of their own heart, and after the Baalim, which their fathers taught them;" — Jeremiah 9:14 (ASV)

Imagination. —Stubbornness, as in Jeremiah 3:17.

Baalim. —The generic name for false gods of all kinds, and therefore used in the plural. (Jeremiah 2:23.)