wife
Explanation
The comic features a character (presumably a linguist or etymology enthusiast) excitedly explaining the word "Winkel" to increasingly annoyed companions. "Winkel" means "angle" in German but "store" or "shop" in Dutch. If you have an English wife whose last name is Winkel and she opens a store on a street corner in Germany, it would be "a Winkel Winkel Winkel." The character continues stacking meanings: it is also an English slang term, also a last name, and if someone is forced to leave their "Winkel Winkel" while something is "open" then it would be "a Winkel Winkel Winkel Winkel Winkel Winkel Winkel." The other character finally slaps the speaker and pleads: "Please, don't do this. I'm not a joke. It's a real life and you're frittering it away." The speaker protests: "I am powerless. So powerless."
The joke is a classic example of the "Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo" style of linguistic humor, where a single word with multiple meanings in different languages or contexts can be stacked to form absurd but technically meaningful sentences. The comedy comes from the escalating absurdity as the speaker keeps finding new meanings of "Winkel" to stack on top of each other, the mounting exasperation of the listener, and the speaker's admission of powerlessness -- they know the joke is terrible but cannot stop themselves. The slap and the plea ("I'm not a joke, it's a real life and you're frittering it away") breaks the fourth wall slightly, with the listener essentially begging to not be trapped in a SMBC comic about wordplay. The humor is self-aware about how insufferable this kind of etymological stacking joke is, while simultaneously being that exact joke.