Why are scientific discoveries rarely named after whoever found them first?

Because credit tends to go to whoever brings an idea to wide attention, or to whoever is already famous, rather than to whoever found it first; and names are often attached long after the discovery itself. In 1980, University of Chicago statistics professor Stephen Stigler gave this pattern a name: Stigler's law of eponymy, stated in its simplest form as 'no scientific discovery is named after its original discoverer.'

The examples pile up fast. Hubble's law was actually derived by Georges Lemaître two years before Edwin Hubble published it. The Pythagorean theorem was known to Babylonian and Indian mathematicians long before Pythagoras. Halley's Comet had been observed by astronomers since at least 240 BC.

Stigler added a knowing twist: he openly credited the idea behind his own law to sociologist Robert K. Merton, which makes 'Stigler's law' itself an example of Stigler's law. Merton had already described something similar with his 'Matthew effect,' the tendency for already-famous scientists to get more credit than lesser-known researchers for comparable work, especially in collaborations or when several people discover the same thing independently.

Why does this keep happening? Often several people arrive at an idea around the same time, as happened with calculus, and whichever version gets the most publicity, or whoever has the most fame already, tends to become the name people remember. Mathematician Vladimir Arnold put it sharply: just as America isn't named after Columbus, mathematical results are almost never named after whoever actually discovered them, which he turned into the Arnold principle; his companion Berry principle adds that the Arnold principle applies to itself.