To understand why, we have to go back to 16th century Scots
While we are all waiting for our jabs, we might wonder why the government is so keen on calling any Covid-19 vaccine a “jab” in the first place. The usage seems at once chummy and infantilising, but why does it mean “injection” anyway?
The verb “jab” is originally a Scottish form of “job”, an onomatopoeic word used since the 16th century to describe the pecking of birds, and then for any poking or thrusting action. (Romantically, “to job faces” with another meant to kiss them ardently.) Hence also the use of “jab” to mean a boxer’s straight punch with the non-dominant hand. (“Jab him, if you can, with your left,” advises a 1901 manual of self-defence by the British boxing champion Robert James “Bob” Fitzsimmons.) The additional sense of mockery or raillery (as in “verbal jabs”) is inspired by this martial context.