sassy

The story

A modification of saucy, equivalent to sass + -y, originally used in American English. First attested in 1799, but in common usage only as of the mid-19th century.

First known use, by meaning

• from 1799 Bold and spirited, often towards someone in authority; cheeky; impudent; saucy.
• from 1861 Smart, fashionable; stylish; chic.
• from 1859 Lively, vigorous.