Judges 8:31

His concubine, ¹  who lived in Shechem, also gave him a son, whom he named Abimelech. ² 

Ge 16:15; Ge 20:2; Ge 22:24; Jud 9:1-5; Jud 9:18

¹ sn A concubine was a slave woman in ancient Near Eastern societies who was the legal property of her master, but who could have legitimate sexual relations with her master. A concubine’s status was more elevated than a mere servant, but she was not free and did not have the legal rights of a free wife. The children of a concubine could, in some instances, become equal heirs with the children of the free wife. After the period of the Judges concubines may have become more of a royal prerogative (2 Sam 21:10-14; 1 Kgs 11:3).

² sn The name Abimelech means “my father is king.”