nomenclator

Etymology

From Latin nōmenclātor (“slave who told master names of persons master met”), from nōmen (“name”) + calō (“call together”).

Why this word is great

NOMENCLATOR — [Noun] An assistant who reminds a person of names and socially important information, or one who assigns names in a classification system. From Latin nōmenclātor ("slave who announced names"), from nōmen ("name") + calō ("to call"). Unlike an "onomastician" (who studies names academically) or a "lexicographer" (who catalogs words), a nomenclator is a practical aide—the whisper in a senator’s ear at a banquet, the curator labeling specimens in a museum, or the bureaucrat stamping files in an archive. It is the act of naming made servile: a flicker of recognition in a crowded room, the crisp typography on a specimen jar, the silent machinery of taxonomy grinding onward—proof that to name is to claim, and to remember is to hold power, however fleeting.

noun

An assistant who specializes in providing timely and spatially relevant reminders of the names of persons and other socially important information.“If he does not know them, it is deception to pretend that he does, while all the time he has never heard of them until instructed by the nomenclator.”
One who assigns or constructs names for persons or objects or classes thereof, as in a scientific classification system.“The nomenclator's method is first to look about and see if the place has any natural features to suggest a name—like Rocking Stone Farm or White Birches.”
A document containing such name assignments.
An early form of substitution cipher.