The term originated in the Roman army and became used thereafter for subaltern officials in the Byzantine Empire, as well as for various positions in the Church, whence derives the English title "dean".
From the 4th century AD the term decanus became used for palace messengers, particularly those in the service of Roman empresses.
Decani also apparently served as guards at gates, and in the 6th century, John Lydus equates them with the ancient lictors.
[2] In the 899 Klētorologion of Philotheos, the decanus (transcribed into Greek as δεκανός, dekanos) was a mid-level functionary, serving under the protasekretis.
[2] In the Christian Church, the term came into use in monasteries for heads of groups of ten other monks, for low-ranking subaltern officials of the Patriarchate of Constantinople, and for the ecclesiastic fossores ("grave-diggers").