Origin uncertain. Compare Middle Frenchbagarot(“noise, tumult, contention, strife”). Perhaps from or related to Old High Germanbāgari(“arguer, fighter”), from bāgan, bāgēn(“to quarrel, dispute”), from Proto-Germanic*bēganą, *bēgijaną(“to fight, contend”), from Proto-Indo-European*bhēǵh-, *bhēgh-(“to press, compel”). If so, then cognate with Germanbägern(“to vex, torment”), Old Norsebágr(“resistance, struggle, fight”).
Alternate etymology cites derivation from Provençal bagarro, possibly from the same origin as above, or from Basque batzarre.