Abimelech means some combination of the words “father” and “king”. We first encounter it in scripture as the name of two Philistine kings in Genesis. Why Gideon named the son of his Ephraimite concubine after the manner of Israel’s oppressors is a bit of a mystery, but Abimelech grew up with aspirations far above his station in life, notions that came not from God but from the nations.
His father had been a judge. Abimelech would be king, or so he determined. He began to plot accordingly.