slang, "perform male masturbation," by 1896, from jerk (v.) denoting rapid pulling motion + off (adv.). Compare come off "experience orgasm" (17c.). Farmer and Henley ("Slang and Its Analogues") also lists as synonyms jerk (one's) jelly and jerk (one's) juice. The noun jerk off or jerkoff as an emphatic form of jerk (n.2) is attested by 1968. As an adjective from 1957.
the legal doctrine of being bound by precedents, Latin, literally "to stand by things decided;" from stare "to stand" (from PIE root *sta- "to stand, make or be firm"). Second element from decidere "to decide, determine," literally "to cut off," from de- "off" (see de-) + caedere "to cut" (see -cide).