Officio
Defined in 2 dictionaries — Black's (1891), Bouvier (1839)
A Dictionary of Law
Henry Campbell Black · 1891
EX, OATH. An oath whereby a person may be obliged to make any presentment of any crime or offense, or to confess or accuse himself of any criminal matter or thing whereby he may be liable to any censure, penalty, or punishment. 3 Bl. Comm. 447.
A Law Dictionary, Adapted to the Constitution and Laws of the United States
John Bouvier · 1839
EX. Vide Ex officto, ‘and 3 Bl. Coin, 447.