> From what I've looked up on the internet my Abernathy ancestors may go back to George Abernethy de Barrie of Scotland.
Negative! You may go back on this side of the Atlantic to the earliest known Abernathy, but any alleged link between any American Abernethy or Abernathy Lineage and George Abernethy of (_not_ de) Barrie was definitively disproved at least 100 years ago. Most Abernathys on this side of the Atlantic, however, seem altogether too unwilling to give up that nice cozy myth.
Bluntly, there is no documentation to support it and lots of evidence against it.