The story
16th-century alteration of clench.
First known use, by meaning
- from 1560s To bend and hammer the point of (a nail) so it cannot be removed.
- from 1716 To make certain; to finalize.
- 1860s To hold a boxing opponent with one or both arms so as to avoid being hit while resting momentarily
Etymology from Wiktionary, CC BY-SA 4.0.