rascally adj.

mid-14c., rascaile "people of the lowest class, the general mass; rabble or foot-soldiers of an army" (senses now obsolete), also singular, "low, tricky, dishonest person," from Old French rascaille "rabble, mob" (12c., Modern French racaille), as Cotgrave's French-English Dictionary (1611) defines it: "the rascality or base and rascall sort, the scumme, dregs, offals, outcasts, of any company."

This is of uncertain origin, perhaps a diminutive from Old French rascler, from Vulgar Latin *rasicare "to scrape" (see rash (n.)) on the notion of "the scrapings." "[U]sed in objurgation with much latitude, and often, like rogue, with slight meaning" [Century Dictionary]. Used also in Middle English of animals unfit to chase as game on account of some quality, especially a lean deer. Also formerly an adjective.

suffix forming adjectives from nouns and meaning "having qualities of, of the form or nature of" (manly, lordly), "appropriate to, fitting, suited to" (bodily, earthly, daily); irregularly descended from Old English -lic, from Proto-Germanic *-liko- (Old Frisian -lik, Dutch -lijk, Old High German -lih, German -lich, Old Norse -ligr), related to *likom- "appearance, form" (Old English lich "corpse, body;" see lich, which is a cognate; see also like (adj.), with which it is identical).