Hadean
The Hadean () is a geologic eon of the Earth pre-dating the Archean. It began with the formation of the Earth about 4.6 billion years ago and ended, as defined by the ICS, 4 billion years ago. , the ICS describes its status as ""informal"". Geologist Preston Cloud coined the term in 1972, originally to label the period before the earliest-known rocks on Earth. W. Brian Harland later coined an almost synonymous term, the "Priscoan period", from "priscus", the Latin word for "ancient". Other, older texts simply refer to the eon as the Pre-Archean.
Ionians
Before then, the Yavanas appear in the Vedas with reference to the Vedic period, which could be as early as the 2nd millennium BC. The Vedas are to be distinguished from the much earlier Vedic period. In the Vedas, the Yavanas are a kingdom of Mlechhas, or barbarians, to the far west, out of the line of descent of Indic culture, in the same category as the Sakas, or Skythians (who spoke Iranian), and thus probably were already Greek. The Ionians of the Aegean are the identity customarily assigned to them.