1) Russian surname 
Abayantsev (Абая́нцев; masculine) or Abayantseva (Абая́нцева; feminine) is a Russian last name, a variant of which is Oboyantsev (Обоя́нцев; masculine) or Oboyantseva (Обоя́нцева; feminine). It derives from the demonym `обоянец` (oboyanets) or, in dialects with akanye, `абаянец` (abayanets), ...