Muss

google

ref

mid 19th century (also as a noun in the sense ‘disturbance or row’): apparently a variant of mess.

wiktionary

ref

Related to mess(“disorder”).

Compare Middle English mus(“a mouse”). See mouse.

etymonline

ref

muss (v.)

"to make untidy, put in a state of disorder," 1837, American English, probably a variant of mess in its sense of "to disorder." It was attested earlier (1830) as a noun meaning "disturbance, state of confusion." Related: Mussed; mussing.