"person, animal, or plant that has been in a country or region from earliest times," 1858, mistaken singular of aborigines (1540s; aboriginal is considered the correct singular in English), from Latin aborigines "the first inhabitants," especially of Latium, hence "the first ancestors of the Romans;" possibly a tribal name, or from or made to conform to the Latin phrase ab origine, which means literally "from the beginning."
This is from ab "off, away from" (see ab-) + ablative of origo "a rise, commencement, beginning, source; descent, lineage, birth," from stem of oriri "arise, rise; be born, be descended, receive life" (see origin). Extended 1789 to natives of other countries which Europeans have colonized, especially "aboriginal inhabitant of Australia." Australian slang shortening Abo attested from 1922 (n.), 1906 (adj.).