It appears from the information provided by the hadith of our Prophet (saas) that Hazrat Mahdi’s (as) name will not be well-known in the run-up to his coming. The only way for his name not to be well-known is the use of a pseudonym. For that reason, Hazrat Mahdi (as) will conceal his own name in the early days of his activities, and will use another name rather than his own.
Mufaddal ibn Umar says: I was in the presence of Imam Abu Abdullah Jaffar-i Sadik, and there were others with me, too. The imam told us, “NEVER MAKE THE NAME OF HAZRAT MAHDI (AS) WELL-KNOWN...” (Sheikh Muhammad ibn Ibrahim Numani, al-Ghaybah al-Numani, p. 174)
Our sheikh Muhammad ibn Ya'qub al-Kulayni relates the same hadith: May Allah increase your salvation, WHAT DOES THE IMAM SAY IN THE HADITH ABOUT THE NAME OF HAZRAT MAHDI (AS) NOT BEING MADE WELL-KNOWN? “DO NOT MAKE HIS (HAZRAT MAHDI’S (AS)) NAME WELL-KNOWN...” (Sheikh Muhammad ibn Ibrahim Numani, al-Ghaybah al-Numani, p. 175)