Origin of name Arkenbright/Ercanbrac etc

Does anyone know the origin of this surname? I have encountered the spellings Arkenbright and Ercanbrac for one and the same person (first name Phoebe, b. in NY state ca. 1830). I am assuming it is of German origin; if so, was there a standard form in Germany that became variously garbled after arrival in the U.S.? I am a professional linguist, so can take a "heavy" technical reply if necessary! I don't have the opportunity to check the GenForum very often; if you can help me, I'd appreciate an e-mail: dick.crum@la.berlitz.comThanks!