Old English alter, altar "altar," from Latin altare (plural altaria) "high altar, altar for sacrifice to the great gods," perhaps originally meaning "burnt offerings" (compare Latin adolere "to worship, to offer sacrifice, to honor by burning sacrifices to"), but influenced by Latin altus "high."

In Middle English, often auter, from Old French auter. The Latin spelling was restored 1500s. As a symbol of marriage, by 1820. Altar-cloth is from c. 1200. Altar-piece is from 1640s; altar-boy from 1772.

mid-15c., presbitori, "bench or seats within the altar rails and reserved for the priests," from Church Latin presbyterium, from Greek presbyterion, from presbyteros "an elder," comparative of presbys "old; old man" (see presby-). In architecture, "the part of the church appropriated to the clergy." Meaning "body of elders in the Presbyterian system" is recorded from 1570s.

"altar top," 1848, Latin, literally "table," also "meal, supper," and "altar, sacrificial table," hence used in Church Latin for "upper slab of a church altar" (see mesa). With a capital M-, the name of an organization for people of IQs of 148 or more founded in England in 1946, the name chosen, according to the organization, to suggest a "round table" type group. The constellation (1763) originally was Mons Mensae "Table Mountain." It is the faintest constellation in the sky, with no star brighter than magnitude 5.0.

La Caille, who did so much for our knowledge of the southern heavens, formed the figure from stars under the Greater Cloud, between the poles of the equator and the ecliptic, just north of the polar Octans; the title being suggested by the fact that the Table Mountain, back of Cape Town, "which had witnessed his nightly vigils and daily toils," also was frequently capped by a cloud. [Richard Hinckley Allen, "Star Names and Their Meanings," London: 1899]

c. 1300, "enclosed space in a church around the altar," from Old French chancel, from Late Latin cancellus "lattice," from Latin cancelli (plural) "grating, bars" (see cancel); the sense was extended in Late Latin from the lattice-work that separated the choir from the nave in a church to the space itself.

ancient southern constellation, 1590s, from Latin āra "altar, hearth," from PIE root *as- "to burn, glow." 

"pile or heap of wood or other combustible materials for burning a dead body," 1650s, from Latin pyra and directly from Greek pyra (Ionic pyrē) "funeral pyre; altar for sacrifice; watch-fire; hearth; any place where fire is kindled," from pyr "fire" (from PIE root *paewr- "fire," source also of fire (n.)). Related: Pyral.

in liturgics, "an antiphon sung as the priest approaches the altar to celebrate mass," late 15c., from Old French introite "(liturgical) introit; entrance" (14c.), from Latin (antiphona ad) introitum, from introitus "a going in, an entering, entrance; a beginning, prelude," past participle of introire "to enter," from intro- "on the inside, within" (see intro-) + ire "to go" (from PIE root *ei- "to go").

"decorated screen behind an altar; brick or stone back of a fireplace," late 14c., rere-dose, from Anglo-French rere-, an archaic combining form of rear (n.), + dos "back" (see dossier). But Klein's sources suggest it is aphetic of Anglo-French areredos, from Old French arere "at the back" (Modern French arrière). For rere-, compare rere-main "a backhand stroke" (c. 1300), rere-supper "a late supper after the ordinary meal."

1530, Tyndale's word (Exodus xxv:30), based on or influenced by German schaubrot (in Luther), literally "show-bread," translating Latin panes propositiones, from Greek artai enopioi, from Hebrew lechem panim, the 12 loaves placed every Sabbath "before the Lord" on a table beside the altar of incense, from lechem "bread" + panim "face, presence." Old English translations used offring-hlafas.

early 14c., "natural or artificial reservoir for water, bathing pool," from Old French piscine "fishpond," from Latin piscina, from piscis "a fish" (from PIE root *pisk- "a fish"). The ecclesiastical sense (also piscina) "stone basin in a church placed close to the altar and used to receive the water in which the priest washed his hands before the celebration of the eucharist" is from late 15c., from Medieval Latin piscina. As an adjective from 1799.