Pigeonhole

Webster's Dictionary of the English Language

·vt To place in the pigeonhole of a case or cabinet; hence, to put away; to lay aside indefinitely; as, to pigeonhole a letter or a report.

II. Pigeonhole ·noun A small compartment in a desk or case for the keeping of letters, documents, ·etc.;

— so called from the resemblance of a row of them to the compartments in a dovecote.