5ME cheveroun < OFr chevron, orig., rafter < VL *caprione < L caper, goat: see CAPRIOLE6
1 a heraldic device in the shape of an inverted V
2 an insignia consisting of a V3shaped bar or bars, worn on the sleeve as of a military or police uniform to show rank or service

I wonder how the etymology went from "goat" to "rafter".