Osismii

The Osismii or Ostimii were a Gallic tribe living in the western part of the Armorican Peninsula during the Iron Age and the Roman period.

Etymology

They are mentioned as Osismi by Caesar, O̓sísmioi by Strabo, Ossismos by Pliny, O̓sismíous by Ptolemy, and as Osismis in the Notitia Dignitatum.
According to Strabo, the Massaliote explorer Pytheas, who travelled to northwestern Europe in the late 4th century BC, reported the variant Ōstimíous, which seems to be the earliest attested form of the name, documented before the Gaulish sound shift -st- > -ss- occurred.
The Gaulish ethnonym Ostimi literally means 'the ultimate', that is to say 'the remotest people', 'those who dwell at the extremity of the Armorican Peninsula'. It derives from the Celtic stem ostim-, itself from an earlier *postim-. In Middle French, the territory they occupied was known as Posterne''.

Geography

The territory of the Osismii was located at the extremity of the Brittany Peninsula, west of the Veneti and Coriosolites.
According to the consensus view summarised by Patrick Galliou, following Pierre Merlat and François Merlet, the territory of the Osismii extended across most of modern Finistère, parts of the Côtes-d'Armor, and slightly into Morbihan. It was bounded roughly from the Gouët estuary at Saint-Brieuc in the north to the Ellé at Quimperlé in the south, a distribution corroborated by the spread of their pre-Roman coinage.
Their chief town was Vorgium, which the Tabula Peutingeriana places at the tip of the Armorican peninsula. Ptolemy names Vorganium as the chief town of the Osismii. However, a milestone from northern Finistère suggests that Vorganium more likely refers instead to Kérilien, which was a different settlement in Gallo-Roman times and makes Ptolemy's identification probably incorrect.
Scholars often attribute the decline of Vorgium to a transfer of capital status. The creation of the Tractus Armoricanus prompted the construction of coastal fortifications against Saxon piracy, shifting strategic priorities toward the coast and leading to the erection of a major castellum at Brest. In the early Middle Ages, Brest appears under the names Civitas Osismorum and Urbs Osismi, probably derived from a 4th-century Osismis mentioned in the Notitia Dignitatum.

History

Early accounts (5th–4th centuries BC)

Some scholars identify the Oestrymnici of Brittany, mentioned in the Ora Maritima of Avianus, with the Osismii. Avianus's poem preserves earlier geographical accounts derived from the voyage of the Carthaginian navigator Himilco in the late 6th–early 5th century BC. If this connection is correct, it would place a people identifiable with the Osismii in Armorica already around 500 BC.
Around 320–300 BC, they are mentioned as Ōstimíous by the Greek explorer Pytheas, whose account is reported by Strabo in the 1st century AD. Pytheas noted that the peninsula projected deep into the Ocean and ended at a headland called Kabaïon, identifiable with either the Point Penmarc'h or the Pointe du Raz. He also mentioned the nearby islands of Ouximasa, which is plausibly linked to Celtic Uxisama and often associated with the toponym ''Ushant.''

Gallic Wars (58–50 BC)

The Osismii submitted to Caesar during the Gallic Wars in 58 BC.
However, they took part in an insurrection against Rome in 56 BC.
In 52 BC, they sent troops to the Battle of Alesia.