wazir

وزير‎ (wazir)

often times AB referred to SE as his Wazir before naming him Guardian, which seems to equate the two terms:

During the days of the Ottoman Empire, the Grand Vizier was the—often de facto ruling—prime minister, second only to the Sultan and was the leader of the Divan, the Imperial Council. "Vizier" was also the title of some Ottoman provincial governors, use of the title often indicating a greater degree of autonomy for the province involved and the greater prestige of the title holder (this was, for example, a major issue in the Bosnian uprising of 1831).

Was Mason Remey the wazir to Shoghi. He did represent Shoghi at state meetings, etc. The IBC seems to be the designated successor to Shoghi and Mason was the wazir of that institution:

Furthermore, wazīr is the standard Arabic word for a government minister. Prime Ministers are usually termed Ra'īs al-Wuzara (literally, President of the Ministers) or al-Wazīr al-'Awwal (Prime "First" Minister). The latter term is generally found in the Maghreb, while the former is typical of usage in the Mashriq(broadly defined, including Egypt, Sudan, Levant, Iraq and the Arabian Peninsula). Thus, for example, the Prime Minister of Egypt is in Arabic a wazīr.

http://en.wikipedia.org/wiki/Vizier

the Wazir was also a term for secretary and lead katib, this might also explain the cultural phenomenon of the Persian Hands turning to Ruhiyyih instead of the IBC immediately after Shoghi's death.