Albert Barnes Commentary 2 Samuel 20:1

"And there happened to be there a base fellow, whose name was Sheba, the son of Bichri, a Benjamite: and he blew the trumpet, and said, We have no portion in David, neither have we inheritance in the son of Jesse: every man to his tents, O Israel." — 2 Samuel 20:1 (ASV)

The son of Bichri... This should be read as "a Bichrite," a name formed in the same way as "Ahohite," "Hachmonite," and so on (2 Samuel 23:8–9). The name comes from Becher, the son of Benjamin (Genesis 46:21; 1 Chronicles 7:6–8).

Saul was also of this family. It is evident that the transfer of the royalty from their tribe to that of Judah still rankled in the hearts of many Benjamites (2 Samuel 16:8 note).