'autochthonous' originates from Greek, specifically the word 'autochthōn', where 'auto-' meant 'self' and 'chthōn' meant 'earth' or 'ground'.

'autochthōn' passed into Late Latin/Medieval Latin as 'autochthonus' and then into English as 'autochthonous' (via scholarly/technical Latin and French influence).

Initially it meant 'sprung from the soil' or 'native to the land', and this core meaning has largely persisted into the modern sense of 'native/indigenous' or 'originating where found.'