Reredos

A reredos (/ˈrɪərˌdɒs, ˈrɪərɪ-, ˈrɛrɪ-/ REER-dos, REER-ih-, RERR-ih-) is a large altarpiece, a screen, or decoration placed behind the altar in a church.

The term reredos may also be used for similar structures, if elaborate, in secular architecture, for example very grand carved chimneypieces.

Reredos is derived through Middle English from the 14th-century Anglo-Norman areredos, which in turn is from arere 'behind' + dos 'back', from Latin dorsum.

(Despite its appearance, the first part of the word is not formed by doubling the prefix "re-", but by an archaic spelling of "rear".)

In French (and sometimes in English by confusing the terms), a reredos is called a retable; in Spanish a retablo, etc.