In the later Western Roman Empire, following the reorganization of Diocletian, a pagus (compare French pays, Spanish pago, "a region, terroir") became the smallest administrative district of a province. By that time the word had long been in use with various meanings. Smith's Dictionary says of it, "The meaning of this word cannot be given in precise and absolute terms, partly because we can have no doubt that its significance varied greatly between the earliest and the later times of Roman history, partly because its application by Latin writers to similar, but not identical, communities outside Italy ..."

Pāgus is a native Latin word from a root pāg-, a lengthened grade of Indo-European *pag-, a verbal root, "fasten" (English peg), 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.