Early 19th century; earliest use found in Maurice Keating (d. 1835), army officer and writer. From Spanish adoratorio pagan temple from post-classical Latin adoratorium place of worship, (pagan) temple from adorator worshipper (late 2nd or early 3rd cent. in Tertullian; from classical Latin adōrāt-, past participial stem of adōrāre + -or) + classical Latin -ium; compare -ory. Compare earlier oratory.

Mid 17th century; earliest use found in Samuel Fisher (bap. 1604, d. 1665), Quaker preacher and writer. From post-classical Latin adoratorius from classical Latin adōrāt-, past participial stem of adōrāre + -ōrius; compare post-classical Latin adoratorium.