AMIN أمين,
Hebrew. An expression of assent said at the conclusion of prayers, very much as in our Christian worship. It is always used at the conclusion of the Suratu ‘l-Fatihah, or first chapter of the Qur’an.
Amin,”Faithful.” Al-Amin is the title which it is said was given to Muhammad when a youth, on account of his fair and honourable bearing, which won the confidence of the people.
Aminu ‘l-Bait, one who wishes to perform the pilgrimage to Makkah.

Based on Hughes, Dictionary of Islam