early 15c., "a criminal hearing of causes," from Anglo-French oyer, Old French oir, oier, from Latin audire "to hear" (from PIE root *au- "to perceive"). Especially in phrase oyer and terminer (early 15c., but from late 13c. in Anglo-Latin and Anglo-French), literally "a hearing and determining," in England a court of judges of assize, in some U.S. states a higher criminal court.
"a work, composition," especially a musical one, 1809, from Latin opus "a work, labor, exertion" (source of Italian opera, French oeuvre, Spanish obra), from Proto-Italic *opes- "work," from PIE root *op- "to work, produce in abundance." The plural, seldom used as such, is opera. Opus Dei, literally "the work of God," is a Catholic organization founded in Spain in 1928 to re-establish Christian ideals in society through examples of the lives of the members.
"sorry for offenses committed, repentant of one's sins, contrite," mid-14c., from Old French pénitent (14c.) and directly from Latin paenitentem (Medieval Latin penitentem) "penitent" (see penitence).
As a noun, "one undergoing penance, a repentant sinner," late 14c., from the adjective (earlier in this sense was penaunt, early 14c., from Old French peneant). Also, in plural, a name distinguishing some Catholic orders, especially those formed for the reception of reformed courtesans.
"licence to print, granted by a licenser of the press," 1640, Modern Latin, literally "let it be printed," the formula of a book licenser, third person singular present subjunctive passive of Latin imprimere "to print, engrave, stamp; press upon, press against," from assimilated form of in- "into, in, on, upon" (from PIE root *en "in") + premere "to press, hold fast, cover, crowd, compress" (from PIE root *per- (4) "to strike"). Originally of state licence to print books, later only of Roman Catholic Church.