1813, "to thrust or strike with a point," a Scottish variant of job "to strike, pierce, thrust," from Middle English jobben "to jab, thrust, peck" (c. 1500), a word of unknown origin, perhaps imitative. Related: Jabbed; jabbing.
1825, "a thrust or poke with the point of something," from jab (v.). Meaning "a punch with the fist" is from 1889. Sense of "injection with a hypodermic needle," once beloved by newspaper headline writers, is from 1914.
he jabbed his finger into her ribs
he jabbed the piece of meat with his pocket knife
he warned me with a jab with his finger