There are people, according to ar-Raazi, who hold to the opinion that the supreme name is a specific name and that people are able to know it. Some of the names suggested, are:

1. Hu or Huwa (He)
2. Allah
3. Al-Hayy, al-Qayyum (The Living, The Everlasting)
4. Dhu’l-jalaali-wa’l-ikraam (The Lord of Majesty and Bounty).
5. The supreme name can be found in the ‘isolated letters’ at the beginning of several Qur’anic chapters (different suggestions are offered).

As Baba Farid, who is one of the most important Chishti Sufis, is holding the third opinion as referred to above, here is what ar-Raazi among other things writes about it:

“It has been reported that Abu ibn Ka’b asked the messenger of Allah (Allah’s blessings and peace be upon him) to teach him the supreme name. He answered: ‘It can be found in these words: ‘Allah! There is no god but He, the Living, the Everlasting’ (Qur’an 2:255) and in these words: ‘A, L, M. Allah! There is no god but He, the Living, the Everlasting’ (Qur’an 3:1-2).

The companions, hearing this, said: ‘It cannot be anything else than the saying Allah! There is no god but He as it can be found in a great number of verses’. But because of the fact that the messenger of Allah has indicated that the supreme name can be found in these two verses, he has taught us that it cannot be anything else than the Living, the Everlasting.”

Fakhraddin Raazi tells this teaching story: Someone asked Ja’far as-Saadiq a question about the supreme name. He answered: ‘First take a bath and purify yourself and then I’ll teach you the supreme name’. The man went into the bath in order to take a complete ablution. At that time, as it was Winter, the water was extremely cold, but every time that the man wanted to leave the water Ja’far ordered his companions to make it impossible for the man to leave the water. They pushed him back several times and his pleading was of no avail. Then he started to believe that they wanted to do something bad and that they wanted to kill him. That is why he asked Allah to help him to escape from their hands. When they heard him say this prayer, they allowed him to leave the water.

Immediately the man said to Ja’far as-Saadiq: ’Teach me now the supreme name of Allah!’ Ja’far gave him this answer: ‘My dear friend! You already have learned the supreme name by which you have implored Allah, and He has answered you by granting what you asked’.

‘How is that?’ the man said. Ja’far then answered thus: ‘No name of Allah, no matter how great they might be, can be useful, if you are invoking Him while your heart remains attached to another than Him. But if you invoke Him while you have lost all your desires and turn only to Him, then the name that you use, is the supreme name. You were thinking that we wanted to kill you and because of that in your heart you only trusted in the grace of Allah. In such a state every name that you invoke, is the supreme name.

http://www.chishti.ru/d_name.htm