Columbarium

Columbarium is defined as "1a. A vault with niches for urns containing ashes of the dead. b. a niche in such a vault. 2a. A dovecote. b. a pigeonhole in a dovecote" (AHD). The word ultimately comes from the Latin word columba, dove (AHD). How does the word shift from meaning "dove" to "a vault with niches for urns" (AHD)? Well, English columbarium is directly borrowed from the same Latin word columbarium, which meant "pigeonhole; niche in a sepulcher" (New College Latin and English Dictionary). Pigeonholes or dovecotes are an extensive complex of man-made compartments for doves or pigeons. In purpose dovecotes resemble chicken coops, in that they house poultry for their eggs and flesh. Columbarium's adaptation to a house for urns stems from its resemblence with the dovecotes. The vault pictured in the top left illustrates this resemblence. Instead of doves, however, the niches hold urns with ashes of the dead.

Photo Source: http://www.neatorama.com/images/2007-01/roman-columbarium.jpg