Amen - (Webster's 1828 Dictionary)
AMEN'. This word, with slight differences or orthography, is in all the dialects of the Assyrian stock. As a verb, it signifies to confirm, establish, verify; to trust, or give confidence; as a noun, truth, firmness, trust, confidence; as an adjective, firm, stable. In English, after the oriental manner, it is used at the beginning, but more generally at the end of declarations and prayers, in the sense of, be it firm, be it established.
And let all the people say amen. Psa 104.
The word is used also as a noun.
""All the promises of God are amen in Christ;"" that is, firmness, stability, constancy.