Pagus

A pagus (plural "pagi") was a Roman and early medieval administrative term designating a rural subdivision of a tribal territory, which included individual farms, villages ("vici"), and strongholds ("oppida") serving as refuges. From the reign of Diocletian (284–305 AD) onwards, the "pagus" referred to the smallest administrative unit of a province. These geographical units were used to define political territories in the Merovingian and Carolingian periods, but then gradually came to be seen as geographical descriptions of counties or shires, without any necessary political or administrative meaning.
Etymology.
Pāgus is a native Latin word from a root pāg-, a lengthened grade of Indo-European *pag-, a verbal root, "fasten", which in the word may be translated as "boundary staked out on the ground". In semantics, *pag- used in pāgus is a stative verb with an unmarked lexical aspect of state resulting from completed action: "it is having been staked out", converted into a noun by -us, a type recognizable in English adjectives such as surveyed, defined, noted, etc. English does not use the noun: "the surveyed", but Latin characteristically does. Considering that the ancients marked out municipal districts with boundary stones, the root meaning is nothing more than land surveyed for a municipality with stakes and later marked by boundary stones, a process that has not changed over the millennia.
Earlier hypotheses concerning the derivation of pāgus suggested that it is a Greek loan from either ', "village well", or ', "hill-fort". William Smith opposed these on the grounds that neither the well nor the hill-fort appear in the meaning of pāgus.
The word "pagus" itself is the stem for Romance languages' words for state or country: "pays" (French), "país" (Spanish) etc.
Roman usage.
In classical Latin, "pagus" referred to a country district or to a community within a larger polity; Julius Caesar, for instance, refers to "pagi" within the greater polity of the Celtic Helvetii.
The "pagus" and "vicus" (a small nucleated settlement or village) are characteristic of pre-urban organization of the countryside. In Latin epigraphy of the Republican era, "pagus" refers to local territorial divisions of the peoples of the central Apennines and is assumed to express local social structures as they existed variously.
As an informal designation for a rural district, "pagus" was a flexible term to encompass the cultural horizons of "folk" whose lives were circumscribed by their locality: agricultural workers, peasants, slaves. Within the reduced area of Diocletian's subdivided provinces, the "pagani" could have several kinds of focal centers. Some were administered from a city, possibly the seat of a bishop; other "pagi" were administered from a "vicus" that might be no more than a cluster of houses and an informal market; yet other "pagi" in the areas of the great agricultural estates ("latifundia") were administered through the villa at the center.
The historian of Christianity Peter Brown has pointed out that in its original sense "paganus" meant a civilian or commoner, one who was excluded from power and thus regarded as of lesser account; away from the administrative center, whether that was the seat of a bishop, a walled town or merely a fortified village, such inhabitants of the outlying districts, the "pagi", tended to cling to the old ways and gave their name to "pagans"; the word was used pejoratively by Christians in the Latin West to demean those who declined to convert from the traditional religions of antiquity.
Post-Roman pagus.
The "pagus" survived the collapse of the Empire of the West, retained to designate the territory controlled by a Merovingian or Carolingian count ("comes"). Within its boundaries, the smaller subdivision of the "pagus" was the manor. The majority of modern French "pays" are roughly coextensive with the old counties (e.g., county of Comminges, county of Ponthieu, etc.) For instance, at the beginning of the 5th century, when the "Notitia provinciarum et civitatum Galliae" was drawn up, the Provincia Gallia Lugdunensis Secunda formed the ecclesiastical province of Rouen, with six suffragan sees; it contained seven cities ("civitates"). For civil purposes, the province was divided into a number of "pagi": the "civitas" of Rotomagus (Rouen) formed the "pagus Rotomagensis" (Roumois); in addition there were the "pagi" "Caletus" (Pays de Caux), "Vilcassinus" (the Vexin), the "Tellaus" (Talou); Bayeux, the pagus Bajocassinus (Bessin, including briefly in the 9th century the "Otlinga Saxonia"); that of Lisieux the pagus Lexovinus (Lieuvin); that of Coutances the p. Corilensis and p. Constantinus (Cotentin); that of Avranches the p. Abrincatinus (Avranchin); that of Sez the p. Oximensis (Hiémois), the p. Sagensis and p. Corbonensis (Corbonnais); and that of Evreux the p. Ebroicinus (Evrecin) and p. Madriacensis (pays de Madrie).
The Welsh successor kingdom of Powys derived its name from "pagus" or "pagenses", and gives its name to the modern Welsh county.
The "pagus" was the equivalent of what English-speaking historians sometimes refer to as the "Carolingian shire", which in German is the "Gau". In Latin texts, a canton of the Helvetic Confederacy is rendered "pagus".