Akkadian

šerˀānu (širˀānu) - sinew, tendon, muscle (CAD Š₂ 308, AHw. 1216)

PS
*ŝVry/w/ˁ-, *ŝVry/ ˁ-ān- - (Achilles) tendon; sinew, muscle (of leg) (SED I No. 268)
A very difficult case (v. SED I).