Stephen A. Kaufman's edition of Targum Onkelos offers an Aramaic paraphrase of Genesis 4:15 that discusses Cain's "mark" or "sign."
Stephen A. Kaufman, ed., Targum Onqelos to the Pentateuch. The Jewish Literary Aramaic version of the Pentateuch from the files of the Comprehensive Aramaic Lexicon Project (CAL) (Hebrew Union College-Jewish Institute of Religion, Cincinnati, USA, 2005), Genesis 4:15. Electronic edition, accessed December 21, 2022
וְשַוִי יוי לְקַיִן אָתָא בְדִיל דְלָא לְמִקטַל יָתֵיה כֹל דְיִשכְחִינֵיה
Etheridge English translation: And the Lord set unto Kain a sign, lest any one who found him should kill him.