Amir, meaning "lord" or "commander-in-chief", is derived from the Arabic root a-m-r, "command". Originally simply meaning "commander-in-chief" or "leader", usually in reference to a group of people, it came to be used as a title for governors or rulers, usually in smaller states, and in modern Arabic is analogous to the English word "prince". The word entered English in 1593, from the French émir. It was one of the titles or names of the Islamic prophet Muhammad.
From the start, emir has been a military title.
In certain decimally-organized Muslim armies, Amir was an officer rank. For example, in Mughal India Amirs commanded 1000 horsemen (divided into ten units, each under a sipah salar), ten of them under one malik. In the imperial army of Qajar Persia:
The following posts referred to "amir" under medieval Muslim states include:
In the former Kingdom of Afghanistan, Amir-i-Kabir was a title meaning "great prince" or "great commander".