Saucy means cheeky, or mildly rude about sex. A saucy remark, a saucy postcard, feeling saucy.
It is one of the most British words on this list: saucy is the register of the seaside postcard and the double entendre, and it is always more amused than shocking. Applied to a child it means impudent. Applied to a look it means flirtatious. Note that saucy comes from sauce, in the old sense of impertinence — the same sense behind none of your sauce.
1adjectivecheekyCheeky or impudent.
“The saucy little boy stuck his tongue out at the teacher and ran off.”
2adjectivesaucyMildly rude about sex.
“The comedian told saucy jokes that made the older ladies giggle.”
saucy is a quality of cheekiness.
Sauce plus -y. Sauce came to mean impudence in the sixteenth century, from the idea of something sharp added to what is served, and saucy is built on that sense.
Proto-Indo-European
*sḗh₂l
Latin
salsus — salted
Vulgar Latin
*salsa
Old French
sause
Middle English
sauce
English
sauce
English, today
saucy
Built from
From sauce + y. sauce comes from Middle English sauce, from Old French sause, from Vulgar Latin salsa, noun use of the feminine of Latin salsus (“salted”), past participle of saliō (“to salt”), from sal. a doublet of salsa. For the meaning development compare ἥδυσμα ultimately from swéh₂dus (whence also sweet).
Etymology from Wiktionary, CC BY-SA