What is the meaning of Autochthon?

The earliest inhabitant of an area; an indigenous person.

A large mass of rock in the place of its original formation, rooted to its basement (foundation rock) as opposed to an allochthon or nappe which has shifted from the place of formation; an autochthonous rock formation.

A term referring to mortals and immortals who have sprung, fully-formed, from the soil, rocks and trees. Mythical characters, such as Erichthonius (a son of Hephaestus and Gaia, and raised by Athena), and Cecrops I, are two most well-known examples.

autochthonous (native to the place where found)

An original inhabitant of a place, a native, an aborigine, an autochthon.

Source: wiktionary.org