Cuppyoid: Acid.

The first known acid was acetum, which the Romans kept in acetabulumi to sprinkle on their moretumi. Eventually they stopped putting up with that sort of thing and started calling it vinum acre, which is to say acrid wine, and the rest is etymology. The French knew a good thing when they tasted it and started keeping vin egre in bouteilles to put on their salades and so today we know acetum as vinegar and keep it in bottles to put on our salads.

As a matter of vague interest, the word science is apparently related to the Sanskrit ch'yati, meaning he cuts off, which is to say slices, while the Latin root ac- that leads from acetum to acid by way of acrid means sharp, while the Greek for unloose gives us analysis, and so it may come as no surprise that the scientist Humphrey Davy (1778-1829) used acid to analyze minerals and eventually got himself a knighthood, presumably complete with sword.

In modern times any substance that's loose with its protons is considered an acid. An acidic substance's dangling proton will bind up with any available electron that happens by; if that electron isn't free, the resulting electron bond can rip bits off whatever substance the electron was being used by, as happened for Humphrey Davy. An acid in contact with some substances — water, for instance — will just lose protons. These free-range protons so fervently aspire to become hydrogen atoms by snapping up any passing electrons that they are generally called hydrogen ions, in the same way that Hollywood residents refer to waiters as aspiring actors. The flip side of acids are substances that snap up dangling protons; these are known as bases or alkalis.

If you were designing a scale to measure acidity-neutrality-alkalinity, you'd probably assign 0 to neutral and then measure outward from there. Instead we got stuck with the pH scale, which measures the intensity or concentration of ionic hydrogen, and is sort of the "PIN number" of chemistry. The H in pH stands for hydrogen, but no one knows what the p means. An experimenter wrote it down, everyone copied him, nobody asked what he meant, and now it's too late. (Some say it stands for power, but have you ever seen a chemist raising his sword and shouting "By the power of Hydrogen!"?) The pH scale runs backwards from 14 (alkaline) to 0 (acid), with 7 being neutral, and experimenters can get out-of-range results on both sides of the scale without even needing to atomic laser matrix to do it.

Acidalia is a town in New York that has nothing to do with acid, actually, being named after a well in Greece filled by the river Acidas. Except that it might have been the river Iardanus, or the river Celadon. But what sense would that make?