"outspoken, impudent, cheeky," 1833, American English, alteration of saucy. Related: Sassily; sassiness.

"impudence, insolence," by 1835, a back-formation from sassy, and ultimately a colloquial pronunciation of sauce. Sass (n.) as a colloquial variant of sauce (n.) is attested by 1775. The verb sass, "to talk or reply saucily, speak impertinently to" is by 1856. Related: Sassed; sassing.