Merriam-Webster's Collegiate® Dictionary, 11th Edition
CHOCK
I. noun
Etymology: origin unknown
Date: 1769
a wedge or block for steadying a body (as a cask) and holding it motionless, for filling in an unwanted space, or for blocking the movement of a wheel, a heavy metal casting (as on the bow or stern of a ship) with two short horn-shaped arms curving inward between which ropes or hawsers may pass for mooring or towing,
II. adverb
Date: 1834
as close or as completely as possible,
III. transitive verb
Date: circa 1841
to stop or make fast with or as if with chocks