unreeve
To withdraw or take out, as for example a rope from a block.
transitive
He could not only splice a broken "fall," and repair the sheaves and friction-rollers in a hoisting-block, but whenever the rigging got tangled aloft he could spring up the derrick like a cat and unreeve the rope in an instant.
Where it comes from
From Middle English *unreven (attested only in past participle unrevyn) equivalent to un- + reeve.
Adapted from the Wiktionary entry unreeve (CC BY-SA 4.0).