Seago does not look very Bavarian or Teutonic to me. The closest I could get would be the name element SIG (victory), but the spelling would be very strange. No name of the kind is listed in Förstemanns "Altdeutsche Rufnamen". But:
The Dictionary of American Family Names, Oxford University Press has SEAGO: English (Norfolk): unexplained. The Oxford Dictionary of Surnames only has Seagot (from sea-god, they say).