It turns out that these phrases are directly tied to our enthusiasm for electricity in the 19th century. As I've written elsewhere, many scientists, doctors, and the general public came to believe that we all had a set amount of electricity in our bodies that made everything run--called our "vital fluid." Modern urban living tended to deplete this energy source according to some leading doctors and scientists, our "internal battery" as the analogy went, and, therefore, we needed a "recharge" from a jolt of electricity. Our bodies were essentially electrical machines that could short-circuit and burn out just like any other machine.
Public enthusiasm for electricity by the late 19th was so great that many came to believe that electricity could fix anything! And waiting in the wings to take advantage of that deep desire were any number of doctors and entrepreneurs promising electrotherapy treatments for every dysfunction or ill-feeling you could imagine. Few in the general public completely understood electricity so they relied on manufacturers of electrical devices to educate them. In a world changing so fast with new inventions and technology, it was hard for anyone to know what was possible and probable. Advertisements for electrical devices made boisterous cure-all promises, and people richly rewarded those manufacturers for giving them what they wanted.
Books, entertainment, and even food of the late 19th century showed that the image of the "electric body" wasn't just a metaphor--people willingly imbibed electricity directly in an attempt to receive all of its benefits. One scientist even compared its effects to that of the sun on the leaves of a plant.
In Europe, researchers studied electricity's effect on school children. They outfitted a classroom with a high-frequency electrical current that ran for six months. At the end of the experiment, the researchers found that the children had grown an average of 20mm more than those not exposed to the continuous current. Their teachers also reported that they had grown smarter during the experiment due to the "quickening" of their faculties by electrical stimulation.
Popular culture teemed with electrical fads and follies, providing both tangible and intangible signs that linked electricity, and especially the electrified human body, with ideas of progress.
While electricity remains part of the treatment regiment for some diseases today, the idea of a vital fluid made of electricity that needs recharging has since passed out of popular and scientific medical theories. But its mark on our language remains.