The word radiator is
a hollow metal device for heating rooms. Radiators are usually connected by pipes through which hot water is sent
But it also has the meaning of
a device for cooling the engine of a vehicle or an aircraft
which is the exact opposite.
1836, "any thing that radiates," agent noun in Latin form from radiate. Meaning "heater" is from 1851; sense of "cooling device in internal combustion engine" is 1900.
But I can't see why radiator is used for a cooling device, too. What is the reason?
Interestingly, since 1900 the use of radiator is massively increased: