The term's origins lie in the 10th century, when senior ministers were sometimes referred to as the (), i.e. 'mediators' between the emperor and his subjects (cf. ). The title first became official in the mid-11th century, when it was conferred on
Constantine Leichoudes, the future
ecumenical patriarch of Constantinople. In the
Komnenian period, it was awarded to senior government officials who functioned as
de facto prime ministers, such as the and the , but had not yet acquired a permanent and specific function, nor the power that would characterize it in later years. Rather, it was a title bestowed on the principal imperial secretary of the moment, who acted precisely as an "intermediary" between the emperor and other officials. This reflected the shift of the Byzantine government under the Komnenoi from the old Roman-style bureaucracy to a more restricted, aristocratic ruling class, where government was exercised within the imperial household, as in
feudal Western Europe. The office of became formally institutionalized in the
Empire of Nicaea, where the holder of the (as the function had become known), served as the Empire's chief minister, coordinating the other ministers. As the emperor and historian
John VI Kantakouzenos () records, the was "needed by the emperor day and night". This arrangement was inherited by the restored
Palaiologan-era Empire and continued in use until the
Fall of Constantinople in May 1453. The office was also used in the same function in the Byzantine courts of
Epirus,
Morea, and
Trebizond. In the latter case, it acquired the epithet ('great'). ==List of ==