Unravel

wiktionary

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From un- +‎ ravel. Compare Dutch ontrafelen(“to unravel”).

etymonline

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unravel (v.)

c. 1600 (transitive), from un- (2) + ravel (v.). Intransitive from 1640s. "The prefix is either reversive or intensive, according as ravel is taken to mean 'tangle' or 'untangle'" [Century Dictionary]. Related: Unravelled; unravelling; unravellment.