According to majority of the Ulema, Aameen is an abbreviation of ‘Allaahummastajib lana” (Oh Allah! Accept our Duaa (supplication))
Nabi (Sallallaahu Alayhi Wasallam) had stated: “I have been granted Aameen (to say) in Salaah and at the time of Du’aa. None was granted such before me except Moosa(Moses) (Alayhis salaam). He would make Du’aa(supplication) and Haroon(Aaron) (Alayhis salaam) would say Aameen. So end your Du’aas with Aameen – Allah will surely answer them for you.” (Tafseer Ibn Katheer Vol.1 Pg.56; Darus salaam). From this Hadith it is apparent that the Jews also are following the sunnah of their Nabi(Prophet) in saying ‘Amen’.
And Allah Ta’ala Knows Best.
By Mufti Bilaal Cassim