The Law of Cosmic Coincidence

The Law of Cosmic Coincidence exists as an explanation for otherwise inexplicable coincidences such as a confederation of merchant city-states on a world within a bubble universe speaking a language that appears remarkably similar to medieval Italian, as spoken on Earth.
In its simplest form, as commonly described in popular books intended for lay-creatures, it can be explained by pointing out that deities and sufficiently powerful supernatural creatures have access to the multiverse and undoubtedly picked up some inhabitants of northern Italian medieval merchant city states in their wanderings and that such individuals, upon finding themselves on a strange and undeniably hostile world, would revert to their native trades and language.
This satisfies most sentient creatures, who weren't particularly interested in the question in the first place, but only asked out of courtesy, having nothing else much to comment on. A small, but highly annoying, subset of the original questioners will persist with the second order question: Yes, but why would they still be speaking it, 6700 years later?
These individuals should be directed to the answer most accepted by philosophers and scientists, which indicates that these types of coincidences are the inevitable result of factors such as the fine structure constant equaling approximately 1/137, the fact that you can never buy two articles of clothing that are exactly the same shade of red, and the delightful discovery that if you plot data with sufficiently large error bars on a log/log graph, you can draw whatever conclusion you like.
The proof of this hypothesis is contained in Volume 1128 of The Encyclopedia of the Realities, a copy of which can be found in the Library of High Sendaris.†
† Those inquiring about the volume at the library will be informed that it is currently checked out and over 1200 years overdue. There is also a wait-list of approximately 3421 years, but they will be glad to add you to the list if you provide three forms of identification.
Extremely persistent visitors to the library are allowed to see a copy of Figure 12482, which had been psychoimaged out of the volume by a Ka weaver/philosopher at some time in the past.

Localization

This law can be found on most worlds, where there is something really awesome from the real world that will fit perfectly, but would require unholy amounts of boring exposition to explain when everyone will know exactly what your source of inspiration was anyway.

Disclaimers

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2) No, I won't share my world with you. At least not yet. This may change as I get farther along.
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