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.
These are all related to the movement of heat and how it gets transferred between substances and locations. Heat can move between objects or spaces, and there are three main ways it does this: conduction, convection and radiation.