"rumpled, disordered, untidy," 1859, from muss + -y (2). Related: Mussiness.
Entries linking to mussy
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.
-y 2
adjective suffix, "full of or characterized by," from Old English -ig, from Proto-Germanic *-iga- (source also of Dutch, Danish, German -ig, Gothic -egs), from PIE -(i)ko-, adjectival suffix, cognate with elements in Greek -ikos, Latin -icus (see -ic). Originally added to nouns in Old English; used from 13c. with verbs, and by 15c. even with other adjectives (for example crispy). Adjectives such as hugy, vasty are artificial words that exist for the sake of poetical metrics.