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"formal public speaking, the art of eloquence," 1580s, from Latin (ars) oratoria "oratorical (art)," fem. of oratorius "of speaking or pleading, pertaining to an orator," from orare "to speak, pray, plead" (see orator).
"small chapel," c.1300, from Old French oratorie and directly from Late Latin oratorium "place of prayer" (especially the Oratory of St. Philip Neri in Rome, where musical services were presented), noun use of an adjective, as in oratorium templum, from neuter of Latin oratorius "of or for praying," from orare "to pray, plead, speak" (see orator).