quite uncertain (cf. Pardee 1985: 66), as long as the meaning suggested by the authors of DUL is accepted, there is hardly any need to postulate a borrowing from Akk. tamšīlu (CAD T 147).
PS
*mṯl - to be similar
(Kogan 2015:236, HALOT 647, AHw. 623, CDG 365)