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 last method heat transfer would be convection. This is the transfer of heat through fluid or air currents. As something heats up, the particles will spread out and thus become less dense. An example of convection would be a pot of water starting to boil on a stove.