A wedge or block used to prevent something from rolling or moving; to fill something completely or wedge something in place.
Possibly from Old French 'choque,' or related to 'shock.' The word may be imitative of the sound of something being wedged in. Used since the 16th century in nautical contexts.
The phrase 'chock-full' is actually 'chock-a-block'—ships would pack cargo using chocks (wedges) until the blocks (ship compartments) were completely full of chocks and cargo, creating a word that literally describes the physical packing method.
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