Sass

google

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mid 19th century: variant of sauce.

wiktionary

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Variant of sauce

etymonline

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sass (n.)

"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.