musk

Musk comes from Middle English muske, from Old French musc, from Late Latin muscus, from Greek móskhos, from Middle Persian muʃk. Behind all of that lies Sanskrit muṣka, meaning 'testicle', a diminutive of mūṣ, 'mouse'.

The name started as a comparison: the gland that produces the scent was likened in shape to a testicle, which was itself likened to a mouse. From that chain of resemblances, the word settled into naming the substance and its smell directly.

It's cognate with English mouse, both tracing back to the Proto-Indo-European word for the animal.