köken: Uncertain, though clearly related to rēx (“king”), itself from Proto-Indo-European *h₃reǵ- (“to rule”). It may derive from an adjective *reg-īno- (“regal, meant for the king”). Sihler instead connects the term with *h₃rḗǵnih₂, which—according to Sihler—perhaps yielded Proto-Italic *rēgnī-, which itself was perhaps remodeled into *rēgnīā according to the model of terms such as avia. Sihler further…