chock (n.) Look up chock at Dictionary.com
1670s, "lumpy piece of wood," possibly from Old North French choque "a block" (Old French çoche "log," 12c.; Modern French souche "stump, stock, block"), from Gaulish *tsukka "a tree trunk, stump."
chock (adv.) Look up chock at Dictionary.com
"tightly, close up against," 1799, back formation from chock-full.