TBESG:πενθερόςfather-in-lawG:N-M πενθερός, -οῦ, ὁ [in LXX chiefly for חָם, Gen.38:13, al.; also for חָתַן, Jdg.1:16 A ;] a father-in-law: Jhn.18:13.† (AS)
πενθερά penthera pen-ther-ah' Feminine of G3995; a wife's motherKJV Usage: mother in law, wife’s mother.