E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Literally, a military oath taken by the Roman soldiers not to desert their standard, turn their back on the enemy, or abandon their general. We also, in the sacrament of baptism, take a military oath to fight manfully under the banner of Christ. The early Christians used the word to signify a sacred mystery, and hence its application to the Baptism and Eucharist, and in the Roman Catholic Church to marriage, confirmation, etc.
The five sacraments are Confirmation, Penance, Orders, Matrimony, and Extreme Unction. (See Thirty-nine Articles, Article xxxv.)
The seven sacraments are Baptism, Confirmation, the Eucharist, Penance, Orders, Matrimony, and Extreme Unction.
The two sacraments of the Protestant Church are Baptism and the Lords Supper.