It comes from the Hebrew word for firm or trustworthy
By the time of the New Testament church, the congregation spoke the word at the end of a public prayer.
So be it.
Let it be done.
In Revelation 3:14, Jesus calls Himself the Amen.
Amen isn’t just a tag at the end of our prayers.
It’s an affirmation that we understand we have asked the Sovereign Lord of all to move on our behalf.
It testifies to our confidence in Him.
It means we are assured of God’s faithfulness, and His character.
So our prayers are heard.