Domestic ("belonging to the house or household") has several ecclesiastical senses:
(1) Domestici are all who belong to the "household of faith."
(2) In the East, the principal dignitary in a church choir after the "chief singer." There was one on each side of the choir, to lead the singers in antiphonal chanting.
(3) Domesticus Ostiorum ("of the doors"), the chief doorkeeper at Constantinople. See Smith, Dict. of Christ. Antiq. s.v.