whip-smart?
I searched it on Google and found another phrase "smart as a whip". I guess both of them mean intelligent but I don't know what "whip" means here. I cannot associate any meaning of "whip" in the dictionary with "smartness" or "intelligence." Could you please help me? Thanks.

Question

Answer

Smart also means energetic and quick in movement - like snapping a whip.  It is a slight play on words.  Smart as a whip means having unusual and quick intelligence.
So the "smart" of a whip - energetic and quick - is replaced by the other meaning of smart - intelligent.

Answer

when somebody gets hit with a whip, we say it really "smarts"  (idiomatic expression)
this is an English expression.  give Sharp pain= "smarts"  it is just an expression we use....

not sure if you are familiar with this