dishevel (v.)

also dishevelled, early 15c., "without dressed hair," parallel form of dishevel, dischevele (adj.) "bare-headed," late 14c., from Old French deschevele "bare-headed, with shaven head," past-participle adjective from descheveler "to disarrange the hair," from des- "apart" (see dis-) + chevel "hair," from Latin capillus "hair" (see capillary). 

Of the hair itself, "hanging loose and throw about in disorder, having a disordered or neglected appearance," from mid-15c. General sense of "with disordered dress" is from c. 1600.