Reganus

Of uncertain origin. Delamarre derives it from Proto-Indo-European *Hreǵʰ- (“to flow water”),^[1] which would connect it to English rain, Albanian rrjedh (“to stream, flow”), but this root does not have any known Celtic descendants, which would be the expected source for the area. Butmann derives it from *h₃reyH- (“to flow”), which would make it related to the river Rhine, but Ferguson finds this derivation "too narrow."^[2]

• (Classical Latin) IPA^(key): [ˈrɛ.ɡa.nʊs]
• (modern Italianate Ecclesiastical) IPA^(key): [ˈrɛː.ɡa.nus]

Reganus m sg (genitive Reganī); second declension

1. The river Regen, in Germany

Second-declension noun, singular only.

• “Reganum”, in William Smith, editor (1854, 1857), A Dictionary of Greek and Roman Geography, volume 1 & 2, London: Walton and Maberly