Initially, it was a term for a military commander it the army of Genghis Khan. (It was not a military rank: the term noyon applied to commanders of tumens (10,000 soldiers), as well as for minghans (1000 soldiers). During conquests noyons used to receive territories for administration and they effectively became Mongolian aristocracy, which existed until the 20th century.
Usually notable persons are referred to with the addition of "Noyan" after the ordinary personal name, similarly to the usage of the title "Khan", e.g., Jebe noyan, Chormaqan Noyan and more.
