jab (v.)
1825, "to thrust with a point," Scottish variant of job "to strike, pierce, thrust," from Middle English jobben "to jab, thrust, peck" (late 15c.), of unknown origin, perhaps echoic. Related: Jabbed; jabbing.
jab (n.)
1825, from jab (v.). Meaning "a punch with the fist" is from 1889. Sense of "injection with a hypodermic needle," beloved by headline writers, is from 1914.