What is the history behind defining temperature as measure of hotness? I know that when two bodies of different temperature are kept in contact "heat" flows from hotter body to colder. But how did anyone know that it is the "hotness" that flows, one could have said that the "coldness" flows from colder body to hotter one. Why was heat given a preference as both cases were equally possible?
I think that the theory that hotness flows from one body to another came long before the kinetic energy theory of energy transfer as heat. Also the caloric theory was given long before kinetic energy theory. In a way everyone knew that it was heat that is flowing and coldness is absence of heat. But how did they know it?
 A: I think the answer is that it is a much more natural physical intuition to say that a hot body has more of something than to say a cold body has more of something. Put a cooking pot on a fire: it is very natural to say that the flames are providing something to the pot, rather than the pot delivering 'anti-heat' to the flames. When water boils, it becomes more active; when it cools the bubbling goes away. Again, the intuition is that the bubbling water has something extra which the still water lacks. So there is a loss of something on cooling. This `something' we now call energy.
A: Temperature, in a way, corresponds to the kinetic energy (vibrational kinetic energy in the case of solids) of the particles that make up the substance. When we bring two substances of different temperatures in contact, the particles with more kinetic energy may bump with the particles of other substance. This collision causes the particles of the colder substances to start vibrating, so in a way, energy from the particles of the hotter substance is transferred to particles of the colder substance. This transfer of kinetic energy is what we refer to as heat. This transfer of energy happens till the system reaches thermal equilibrium (overall the kinetic energy of all the particles should approximately be the same). 
We can see the energy is transferred from particles with high kinetic energy to the particles with low kinetic energy, that is, heat flows from hot body to a cold body. 
There's nothing wrong in saying "coldness" flows from cold body to hot body but the reason as to why we don't use this analogy quite often is because "coldness" is just absence of energy being transferred (which might not make any sense) while "hotness" or heat is the presence of energy being transferred, so it feels as if "something" is being transferred. 
I hope you got what I'm trying to convey.
