Stigler’s law of eponymy says that no scientific discovery is named for its original discoverer. Notable examples include the Pythagorean theorem, Occam’s razor, Halley’s comet, Avogadro’s number, Coriolis force, Gresham’s law, Venn diagrams, Hubble’s law…
Statistician Stephen Stigler coined this law in a 1980 festschrift honoring sociologist Robert K. Merton. It was Merton who had remarked that original discovers never seem to get credit. Stigler playfully appropriated the rule, ensuring that Stigler’s law would be self-referential.
The generalization is not limited to science. Elbridge Gerry did not invent gerrymandering, nor Karl Baedeker the travel guide. Historians of rock music trace the lineage of the Bo Diddley beat, which didn’t originate with that bluesman. The globe is filled with place names honoring explorers who discovered places already well known to indigenous peoples (Hudson River, Hudson Bay; Columbia, District of Columbia and Columbus, Ohio; etc. Perhaps there are extraterrestrials who would consider the Magellanic Clouds a particularly egregious example).
Béchamel sauce is named for a once-famous gastronome, causing the rival Duke of Escars to complain: “That fellow Béchamel has all the luck! I was serving breast of chicken à la crème more than twenty years before he was born, but I have never had the chance of giving my name to even the most modest sauce.”
Stigler’s law is usually taken to be facetious, like Murphy’s law (which predates Edward A. Murphy, Jr., by the way). It is facetious in its absolutism. But it says something non-trivial about the nature of discovery and originality.
The naive take on Stigler's law is that the "wrong" people often get the credit. It's true that famous scientists, and others, sometimes get disproportionate credit relative to less famous colleagues. (That's actually a different law, the Matthew effect.)
What Stigler's law really tells us is that priority isn't everything. Edmund Halley's contribution was not in observing the 1682 comet but in recognizing that observations going back to 1531 (and millennia earlier, we now know) were of the same periodic comet. This claim would have made little sense before Newton's law of universal gravitation. Halley's achievement was developing the right idea at the right time, when the tools were available and the ambient culture was able to appreciate the result. Timeliness can matter as much as being first.