A wicked or cruel person; a devil or demon; also, an enthusiast obsessed with something.
From Old English 'feond' meaning 'enemy' or 'demon,' related to 'foe.' The root likely connects to a Proto-Germanic word meaning 'hostile.' The modern slang use (like 'coffee fiend') is more recent.
The word 'fiend' meant 'enemy' in Old English—your fiend was literally someone who wanted to harm you. Over time, it got more dramatic and supernatural (demons, devils), and now we use it casually for anyone obsessed with something ('Netflix fiend').
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