At first it was used to refer to an officer whose rank was below court noble, but later on came to be used for other responsible parties in charge of practical affairs, such as a Kurodo (Chamberlain), Benkan (Oversight Department - a division of the "daijokan" which was responsible for controlling central and provincial government offices), and Geki (the Secretary of the Grand Council of State).
当初は責任者である公卿以下の官人を指したが、後には実務を担当する蔵人・弁官・外記などを指すようになった。