foolishness
UK: ˈfuːlɪʃnəs | US: ˈfuːlɪʃnəs
n. the quality or state of being foolish; lack of good sense or judgment
The word "foolishness" combines "foolish," derived from Middle English "folish," meaning "lacking wisdom" (itself from "fool," tracing back to Old French "fol" and Latin "follis," originally meaning "bellows" but later metaphorically "empty-headed person"), with the suffix "-ness," from Old English "-nes," used to form abstract nouns denoting a state or condition. The progression reflects a shift from literal emptiness (bellows) to metaphorical lack (fool) to an abstract quality (foolishness).
His foolishness led to a costly mistake.
She regretted the foolishness of her impulsive decision.
The plan was dismissed as sheer foolishness.
Wisdom often comes after years of foolishness.
They laughed at the foolishness of the prank.