gens

Gens, gentis, f., third declension i-stem, genitive plural gentium. The root is gigno, "beget", so the idea underneath is descent.

Start narrow. A Roman gens is a clan sharing a nomen and a claimed ancestor - the Iulii, the Cornelii, the Fabii - and it is a legal unit, not a sentiment. From there the word widens to tribe, then to a whole people, and ius gentium is the body of law the Romans thought common to all peoples. In the Vulgate the plural gentes renders the Greek ethne and means the Gentiles, the nations outside Israel, which is where English gentile comes from; gentle and genteel come from the same word by a different road, through the sense "of good family". Ubinam gentium, "where in the world", uses a partitive genitive that looks strange until you see it a few times.