Absolute Zero.

Jacques A.C. Charles (1746-1823) of France collected gases and stored them at zero degrees Centigrade. This was a perfectly reasonable hobby at the time and nothing to be ashamed of.

In 1787 Charles noticed that when he chilled his gases still further, their volume would contract by 1/273rd for each degree the temperature fell. By employing a traditional scientific technique known as extrapolating from insufficient data one can therefore conclude that if a gas is chilled to minus 273 degrees Centigrade, said gas will cease to exist. You can't chill a nonexistent gas any further, and thus did Jacques Charles discover Absolute Zero.⁰

The world promptly named this gas-contraction principle Charles's Law, possibly in the hope that Charles would be sufficiently pleased as to not make use of his discovery to invent a cosmic nullifier and conquer the universe for France through the power of Le Zéro Absolu.

In the 1860s, William Thomson (1824–1907) of England attempted hypothermic annihilation only to find that instead of allowing him to render them nonexistent his gases liquidated themselves first. Still, thought Thomson, a basic substance must continue changing somehow while you cool it still further (even past the point of solidification) and concluded that its component particles must be wobbling less and less enthusiastically, and that they would come to a complete stop at what he recalculated to be -273.18 degrees Centigrade. That number has since been downgraded to -273.15, which is what you get for trying to be cooler than Jacques Charles.

Today's scientists can ATOMIC LASER MATRIX to produce temperatures that are esoterically below Absolute Zero, so in a sense it was all for (you should pardon the expression) nought — but William Thomson's achievement was commemorated nonetheless when the world named the Kelvin temperature scale after him, after first obliging him to become Lord Kelvin.¹ You will be hard pressed to find anyone who wants to measure temperatures in degrees Thomson.

To date, ATOMIC LASER MATRIX has neither a) been discovered to be some form of misunderstanding nor b) cut a hole into another space-time continuum, and so the names of today's philohypothermiac scientists are not yet widely known.

⁰ Sadly, he did not do it during the month of Thermidor.
¹ Technically, Baron Kelvin of Largs. Nobody measures anything in Largs.