 The Late Latin title "campi doctor" or "campi doctus" (literally "teacher of the [military] field"), rendered "campeador" in Castilian Romance, is first applied to the Cid by the anonymous author of the "Carmen", and it may be his literary invention.The library of Ripoll may have contained references to the obscure fourth- and fifth-century Roman military usage.It is not known how the term, which originally indicated a "regimental drill-instructor", came to currency in eleventh-century Spain, with a meaning like "armiger".