In a manner that shows a lack of good sense, judgment, or wisdom; stupidly or unwisely.
From 'fool,' originally from Latin 'follis' meaning a bag or bellows, later referring to someone who was inflated with pride but empty of sense. The '-ly' suffix creates the adverb form.
Court jesters were professional 'fools' who could say truthful things that would get others executed, because people expected them to talk nonsense—making foolishness a strategy for speaking truth to power.
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