'Foolishness' in the Bible

I said of laughter, "It is foolishness;" and of mirth, "What does it accomplish?"

I turned around, and my heart sought to know and to search out, and to seek wisdom and the scheme of things, and to know that wickedness is stupidity, and that foolishness is madness.

The beginning of the words of his mouth is foolishness; and the end of his talk is mischievous madness.