אָמֵןamen meaning in Biblical Hebrew
truly, so be it — a binding 'yes, I accept the terms' · particle (affirmation)

You think amen is the polite period at the end of a prayer. In the Bible it's a signature on a contract — say it and you just accepted liability, curses included.
וְעָנָה כָל־הָעָם וְאָמַר אָמֵן
“And all the people shall answer and say: Amen. (Deuteronomy 27:15)”
When did you last say amen as a real yes, not just the end of someone else's prayer?
Biblical Hebrew words for worship and the TempleBiblical Hebrew words for covenant and promise