potable
Explanation
This single-panel comic is set in what appears to be a medieval tavern. A person stands on a table addressing the crowd, declaring: "Okay, new rule! Whenever the local water supply may be contaminated with bacteria that cause cholera or dysentery but can be made potable by the antiseptic properties of alcohol... YOU TAKE A DRINK."
The caption reads: "Medieval drinking games were more practical."
The joke reframes the well-known historical fact that people in medieval (and earlier) periods often drank beer and wine instead of water because the alcohol content helped kill waterborne pathogens. Brewing and fermentation processes also involved boiling, which further sterilized the liquid. This was a genuine public health practice -- low-alcohol "small beer" was a daily staple for adults and even children.
The comic reformats this historical reality as a drinking game rule, complete with the rowdy, frat-party energy of someone standing on a table and shouting the rules. The humor comes from the collision between the modern concept of a "drinking game" (a frivolous social activity built around arbitrary rules) and the medieval reality where drinking alcohol was literally a survival strategy against deadly waterborne diseases. The "rule" being announced is not arbitrary at all -- it is medically sound advice that could save lives. The word "potable" (meaning safe to drink) adds a layer of humor by being an unusually technical and formal word for a rowdy tavern announcement, and also neatly connects to the comic's slug/title.