1.
boss; ringleader; organizer
The person who controls or manages an operation from behind the scenes. Often implies the top figure in an organization, especially one with shady or informal power structures.
Originally referred to the person who controlled the source (元) of goods or money. In Edo-period Japan, it denoted the head of a trade guild or the person who managed the distribution of licensed goods.
In modern usage, the word often carries a negative connotation, suggesting someone who pulls the strings behind an illegal or semi-legal operation. However, it can also be used neutrally for anyone who is the central organizing figure of an activity.