The Hebrew text uses "nabal" and implies wilting or immorality. Through many centuries of loose translation it has come to be associated directly with foolishness(Latin:follis). Had the original Hebrew text writers meant to imply "fool" as we know it today they would have more likely used the word "kesil". In Matthew 5:22 the Greek text uses both "raka" and "mwroj". The latter gives root to the contemporary expressions of both "moron" and "morose". The former, "raka", is what I believe to be the closest of Biblical terms referenced here to that which is alluded to by Michael in this post as "The Fool".