What does the phrase “a shot in the arm” mean and Where does it come from?

The phrase “a shot in the arm” was derived from the hypodermic injection of a drug administered by a physician for the prevention or cure of a disease or the alleviation of pain.

To be sure, the expression is used with such meaning, but we don’t think that the original “shot” was with such purpose.

It was administered by a hypodermic syringe, all right, but with a “Quick, Watson, the needle!” intent, the injection of any drug that would induce exhilaration.

In our opinion, the expression, which is not more than about forty years old, was derived from drug addiction, though it is applied now, not only to medical injections as for vaccination, etc., but also to the taking of any stimulant, such as coffee, a “Coke,” or an intoxicant, in the latter instance replacing the older “shot in the neck.”