"superlatively sacred or inviolable," c. 1600, from Latin sacrosanctus "inviolable, protected by religious sanction, consecrated with religious ceremonies," from sacro, ablative of sacrum "religious sanction, religious rite" (from neuter singular of sacer "sacred") + sanctus, past participle of sancire "make sacred" (for both, see sacred). Earlier in partially Englished form sacro-seint (c. 1500).
late 14c., religiosite, "religious feeling, reverence for God, piety," from Old French religiosete and directly from Late Latin religiositas "religiousness," from religiosus "pious, devout, reverencing or fearing the gods," also "religiously careful, anxious, or scrupulous" (see religious). In late 19c. especially "religious sentimentality, excessive susceptibility to religious emotion without corresponding regard for divine law."
"one who conducts a religious service, one who administers a sacrament," 1836, from noun use of Medieval Latin officiantem (nominative officians) "performing religious services," present participle of officiare "to perform religious services," from Latin officium "a service; an official duty; ceremonial observance" (in Medieval Latin, "church service"); see office.