Where does “木什” come from?

木什 (Chinese) comes from Turkish Muş, from Persian موش, from Middle Persian mwšk', from Sanskrit मुष्क, from Sanskrit मूष्, from Proto-Indo-European múh₂s — mouse.

Ancestry of “木什”, step by step

Step	Language	Word	Meaning
1	Turkish	Muş	A sightseeing boat
2	Persian	موش	mouse; rat
3	Middle Persian	mwšk'	musk
4	Sanskrit	मुष्क	testicle, scrotum
5	Sanskrit	मूष्	mouse; "stealer", "thief"
6	Proto-Indo-European	múh₂s	mouse

Every word from Proto-Indo-European múh₂s →Every word from Sanskrit मूष् →Every word from Sanskrit मुष्क →