Droungos

Droungos (Greek: , sometimes δρόγγος, "drongos") or drungus is a late Roman and Byzantine term for a battalion-sized military unit, and later for a local command guarding mountain districts. Its commander was a " or " (δρουγγάριος), anglicized as "Drungary".
History and functions.
The term is first attested in Latin in the late 4th century AD. It derives from Gaulish * (see Old Irish ; Old Breton or ), meaning "tribe", "group", "throng" or "crowd". An alternative Germanic etymology () cited by some historians, originates in 17th-century guesswork which has been rejected by the overwhelming majority of philologists. The earliest usage of in Latin is non-technical and similarly signifies a generic "band" or "troop", which Vegetius equates to Latin .
The term first occurs in Greek as () or (δρόγγος), with the same meaning, in the early 5th century. In the late 6th century, the Emperor Maurice (r. 582–602) applies to a specific tactical deployment, usually of cavalry, characterised as a compact non-linear grouping suited to outflanking tactics, ambushes and irregular operations. He is the first author to employ the cognate adverb (Greek: δρουγγιστί), with the sense of "in group formation" or "small-group tactics". Maurice also occasionally employs as a generic expression for larger "groupings" or "formations" of troops, though in this sense he refers only to a "division" () and never to a "brigade" () with which became associated in later sources. 
By the middle of the 7th century, this meaning had been superseded by a new meaning, which it held until the 11th century. The , alternatively known as a (μοίρα), was now formalized as a regular subdivision of a "tourma", the chief subdivision of the new "themata" (θέματα, singular: θέμα). In turn, each was composed of several "banda" (singular: "bandon"). Thus each or was the analogue of a modern regiment or brigade, initially circa 1000 men strong (and hence also referred to as a "chiliarchia"). On occasion, it could rise to 3000 men, and Emperor Leo VI the Wise (r. 886–912) is recorded as having established of only 400 men for the new smaller themes created during his reign.
From the late 12th century onwards, the term was applied to mountainous areas in Greece, and was associated with the meaning of "pass" or "mountain range" ("zygos"). In the 13th century, it also came to designate the military units detailed to guard these locations, similar to the earlier "kleisourai".