To cause someone persistent trouble, annoyance, or confusion; to harass or frustrate.
From be- (prefix meaning to make or cover with) + devil. Originally meant literally to possess with a devil or behave demonically, but evolved to mean any kind of persistent trouble or frustration.
Bedevil perfectly captures how language evolves—it started as spiritual language about actual demonic possession, then became metaphorical for any nagging problem, showing how religious concepts become everyday speech.
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