pewH-bʰl-mn̥-
“the people, public body”people, popular, population, republic
Nominal yielding Latin populus, English people, popular, population, republic.
Discussion
The Proto-Indo-European form *pewH-bʰl-mn̥- is a complex derivative reconstructed with the approximate meaning "the people, the multitude" and ultimately traces back to the root *pewH- "to be full, to teem" or possibly *pew- "few, small" (the exact analysis is debated). The formation, whatever its precise morphological breakdown, produced one of the most important political and social terms in Western civilisation.
In Latin, the form developed into populus "people, nation", which gave English people (through Old French peuple), popular, populace, population, and depopulate. The Latin adjective publicus "of the people" (contracted from populicus) produced English public, publish, republic (res publica "the people's affair"), and publicity. The word pub is a shortening of "public house", making even this humble term a distant descendant of the Proto-Indo-European root.
The distinction between populus (the people as a political body) and plebs (the common people) was fundamental to Roman social organisation, and the English derivatives preserve this distinction: popular versus plebeian carry different connotations inherited from Roman class structure.
The word republic deserves special attention. Res publica literally means "the public thing" or "the people's matter" — a concept so important to Western political thought that it has been borrowed into virtually every European language. The idea that governance belongs to the people (rather than to a king or god) is encoded in this Proto-Indo-European derivative.
Outside Latin, the root is less clearly attested, and some scholars regard populus as an Italic innovation rather than a direct Proto-Indo-European inheritance. The Etruscan word for "people" has been proposed as an alternative source, though this remains highly speculative.
Whether inherited from the proto-language or coined in Italic, the descendants of this form — people, public, republic, popular — constitute some of the most consequential words in the history of political thought.