This is because Hg is an abbreviation of the Latin name of the element, which was hydrargium. With this name the Greeks were referring to the fact that mercury is a silvery liquid at room temperature, rather than a solid like other metals.
We've looked at the three types of heat transfer. Conduction and convection rely on temperature differences; radiation does, too, but with radiation the absolute temperature is important.
(The amount of energy radiated increases quickly at higher temperatures.) The three methods of heat transfer are: (1) Conduction - particles bump into other particles, transferring energy. (2) Convection - moving masses carry heat with them.