Lewis & Short

prīmĭvirgĭus, ĭi, m. [primus-virga], one who carries the rod first before the king, head verger: πρωτοραβδοῦχος, primivirgius, Gloss. Gr. Lat.: primivirgius, caballarius, quod primus est militiae in virgis, Gloss. Isid.