The etymology of the term
or [n-r-g], is from Greek ενέργεια, εν-
means "in" and έργον means "work"; the -ια
suffix forms an abstract noun. The compound εν-εργεια
in Epic Greek meant "divine action" or "magical
operation"; it is later used by Aristotle in a meaning
of "activity, operation" or "vigour", and by Diodorus
Siculus for "force of an engine"