At first they used "measures of hotness", but ran out a few generations in. Coincidentally, degrees of warmth are all named after scientists. So they continued with scientists.

https://en.m.wikipedia.org/wiki/Fahrenheit_(microarchitectur... -> https://en.m.wikipedia.org/wiki/Celsius_(microarchitecture) -> https://en.m.wikipedia.org/wiki/Kelvin_(microarchitecture) -> https://en.m.wikipedia.org/wiki/Rankine_(microarchitecture)