Perhaps from gerah; a grain; Gera, the name of six Israelites -- Gera.
see HEBREW gerah
H1617. Gera
גֵּרָא proper name, masculine (Phoenician גרא) son of Benjamin Genesis 46:21 (lacking Numbers 26:38-40); son of Bela`, & grandson of Benjamin, according to 1 Chronicles 8:3, 5 compare 8:7; designation of a Benjamite family or clan; hence Ehud called בֶּןגֵּֿרָא Judges 3:15, & so Shimei, 2 Samuel 16:5; 19:17; 19:19; 1 Kings 2:8.
גרב (√ of following; Arabic , Aramaic (have the scab etc.), are apparently denominative)