From an unused root meaning to smear; plaster (as gummy) or slime; (figuratively) frivolity -- foolish things, unsavoury, untempered.
H8602. taphel
I. תָּפֵל adjective tasteless, unseasoned; — absolute ׳ת, as substantive Job 6:6; figurative of unsatisfying prophecies Lamentations 2:14 ( + שָׁוְא).
II. תָּפֵל noun [masculine] whitewash; — applied to wall, in Ezekiel's vision Ezekiel 13:10-11, 14, 15; figurative of false prophet 22:28.