רב אחא אחוהי דאבא

Rab Achah, the brother of Abba, the father of Rabbi Yirmiyah bar Abba, said about him [(and some say about Abba, his brother, in his name)] that he was a penitent in the days of Yoshiyahu in his generation. And he is simply referred to as Rab Achah. [And I do not know from where this is derived.]