Nomenclâtor, pen. prod. nomenclatôris, m. g. vel. vt quibusdam placet. Nomenculâtor. A bedill or like officer to whom it belongeth to know by heart the names, offices, and craftes of all the citizens, thereby to instruct such as among the Romanes did stand and labour for any office, that they might speake to them more gently.
Lewis and Short: Latin dictionary
nōmenclātor (nōmencŭlātor, Mart. 10, 30, 23; Suet. Aug. 19; id. Calig. 41; id. Claud. 34), ōris, m. [id.], one who calls a person or thing by name, a nomenclator; among the Romans, a slave who attended his master in canvassing and on similar occasions, for the purpose of telling him the names of those he met in the street, Cic. Att. 4, 1, 5; id. Mur. 36, 37: nomenclatori memoriae loco audacia est, Sen. Ben. 1, 3, 10; id. Ep. 19, 11; id. Ben. 6, 33, 4.—Under the emperors, a slave who told his master the names of the other slaves: servorum causā nomenclator adhibendus, Plin. 33, 1, 6, 26.