[david-given]

The business about the fever is a myth. Fahrenheit's original fixed points were a mixture of ice, water and ammonium chloride, at 0, and normal human body temperature --- at 96. He then redefined it in terms of the freezing point of water and human body temperature, at 32 and 96, so as to have 64 degrees between them.

After his death in 1776, it was redefined based on the freezing and boiling points of water at STP, at 32 and 212 (a difference of 180). So in fact it uses the same fixed points as Celsius, and has for hundreds of years.

Also, you have Celsius and Kelvin backwards: Kelvin was originally formulated to use the same sized degrees as Celsius, not the other way round. Celsius was first. (Although Celsius is now defined in terms of Kelvin.) See also Rankine, which is the Kelvin equivalent to Fahrenheit: absolute zero is 0, the freezing point of water at STP is about 492, and boiling point is about 671.

Did you know that the original Celsius scale ran from 0 at boiling point to 100 at freezing point, i.e. backwards? It was reversed after his death. Fahrenheit didn't make that mistake!