“Old man” Fahrenheit???
He died at 50! He never got anywhere near to being an “old man”… 
OK, so did anyone ever discern a reason that the Celsius (or Centigrade, if you prefer) scale was originally created upside down?
Celsius did his work long before Charles, Gay-Lussac, or Joule did their fundamental work on the nature of heat. At the time, it made as much sense to put an essentially arbitrary scale one way as the other.
The ancient Greeks spoke of “high” and “low” musical notes, and meant the opposite of what we do.
According to Wikipedia, Celsius did a lot of work relating to the boiling point of water at different pressures, so it makes sense that to him, water’s boiling point should be zero. Makes the math easier anyway.