Did you know [the word] “Mahdī” is one of the most famous sobriquet of Imām Mahdī (mgehr)?
Did you know the word “Mahdavīat” is most popular [sobriquet] amongst Sunnis?!
In narrations, the sobriquet “Mahdī” is often used about The Excellency [Imām Mahdī (mgehr)] after the emergence and “Qāʾim” is used before the emergence.
Imam Baqīr (pbuh) said, “He was called Mahdī, because he is guided via the unseen affair [Divine way].
He will exploit Torah and other Divine books from a cave in Antioch (in Turky).”
‘Ilal al-Sharāyi’, vol. 1, p. 161; Al-Ghaybah, p. 237
Darsname-ye Mahdavīat, vol. 1, p. 235