"Prophet (saw) kept the name of Mahdi secret Jabir quotes from Abu Ja’far: “When Umar asked Hazrat Ali (ra) about Mahdi, he (Umar ra) said: Ibn Abu Talib (Hazrat Ali), tell me about Mahdi. What is his name?” And Hazrat Ali (ra) said: “My dear, close friend, our Prophet saw) said: “Allah had me promise not to reveal his name to anybody until he would appear. His name is one of the knowledge which Allah entrusted upon his messenger. (Iqmal al-Din) (Gaybah, Allame Muhammad Baqir Majlisi, Ansariyan Publishing, Iran, 2007)"

-