Question

phrase meaning of "have you never heard that a fool may teach a wise man wit"

Answer 1

This is called a maxim or a kind of aphoristic or proverbial statement that comes with an ulterior layer of teaching.

In any case, this means how even apparently fool people can teach wise people to learn new things in life.

Fools might not be underestimated as they can be better seers at times, and might teach even a wise man how to be witty.