Akkadian

giššu (gilšu) - hip, flank (CAD G 73, AHw. 288)

giššu is found in the majority of contexts; -l- in gilšu may be the scribal effort in order to render laterality

PS
*giŝŝ- - torso, body (SED I No. 97)
The protoform *giŝŝ- is supported by Akk., Arm., Arb. Daṯ. and presumably MSA.