The term's origins lie in the 10th century, when senior ministers were sometimes referred to as the mesiteuontes (μεσιτεύοντες), i.e. "mediators" between the emperor and his subjects (cf.
The office of mesazōn became formally institutionalized in the Empire of Nicaea,[REF] where the holder of the mesastikion (as the function had become known), served as the Empire's chief minister, coordinating the other ministers [REF].