The term 'PHYSICIST's Unit' is composed of two abbreviations: ERG and RAD. ERG stands for 'ergs, ' a unit of energy or work, and RAD stands for 'radiation absorbed dose, ' which is a measure of the amount of radiation absorbed by an object. Ergs are used to measure the amount of energy released or expended in a given process, while radiation absorbed dose is used to measure the amount of radiation that has been absorbed by a material. Together, these two units are used to measure the amount of energy released or absorbed by a material during a process.