Sadr (title)
Sadr was primarily used in the Iranian world to designate an exceptional person, such as a scholar. It was initially used as a personal title for major religious scholars in Transoxiana, then also for high-ranking administrative figures, and from  until the late 18th-century, for the head of the religious authority of a nation. It was then ultimately used for high-ranking figures in Qajar Iran, including the grand vizier. References

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Titles in Iran