Albert Barnes Commentary Jeremiah 20:3

"And it came to pass on the morrow, that Pashhur brought forth Jeremiah out of the stocks. Then said Jeremiah unto him, Jehovah hath not called thy name Pashhur, but Magor-missabib." — Jeremiah 20:3 (ASV)

Magor-missabib - See Jeremiah 6:25 note. Jeremiah uses it no less than five times, having probably adopted it as his watchword from Psalm 31:13.