ur
Explanation
The Joke
A character explains an interesting linguistic fact: "Ur" can be used to refer to the original version of something (as in "the ur-text" or "the ur-example") because "Ur" was historically considered the name of the first city — the ancient Sumerian city of Ur in Mesopotamia.
However, a second character points out that Ur was not actually the first city — there were earlier cities. This leads to a recursive linguistic problem: if "ur" means "the original" but Ur itself was not the original city, then the correct term for the actual original city would need a prefix denoting something even more original than "ur." This spirals into absurdity, with suggestions like "the ur-ur" or similar constructions, each layer attempting to get back to the truly original thing.
The joke escalates as the characters get tangled in the recursive loop, with the conversation itself becoming an example of the kind of pedantic linguistic spiral that academics fall into. The final panels show one character becoming exasperated with the whole exercise, possibly calling it an "ur-error" — an error about the concept of "ur" that is itself the original form of a particular type of error.
The Humor
The comedy works on multiple levels. First, there is the straightforward humor of linguistic pedantry spiraling out of control. Second, there is the meta-humor of the argument becoming self-referential: the debate about what counts as "original" becomes its own original example of a certain type of futile debate. Third, there is the irony that the prefix "ur-" (meaning original or primordial) is itself based on a factual error about what was truly original, undermining the very concept it tries to express.
Broader Context
The prefix "ur-" entered English from German, where it means "primordial" or "original" (as in "Urtext," meaning the original text of a work). It is often associated with the ancient Sumerian city of Ur (modern-day southern Iraq), one of the earliest known cities, dating to around 3800 BCE. However, settlements like Eridu, Catalhoyuk, and Jericho have claims to being older. The comic plays on the tension between etymology and historical accuracy — a favorite SMBC theme.