become more mentally alert, able, inventive or cunning
A silent person reserves all this energy and utilises it for a better purpose, be it to sharpenhisbrain or memory power for which all the educated yearn for. Google
Adversity merely serves to sharpenhis wits and he is always busy cooking up some scheme. Google
Petruchio is the kind of man who would want a mate with similar qualities to his own to challenge him, sharpenhiswits and keep his interest. Google