Tiberis

Latin

A pre-Roman name, suggested origins include:

From Proto-Italic *Tiβeris. Cognate with Faliscan *Tiferis (cf. Etruscan praenomen Thefarie < Faliscan *Tiferios (“(He) from the Tiber”), equivalent to Latin Tiberius).^[1] *Tiβeris and *Tiferis may come from the same root as temerō, from Proto-Italic *temezi (“in darkness, blindly”), a fossilised locative form of Proto-Indo-European *témHos (“darkness”), from *temH- (“dark”). See Thames.
From Celtic *dubros (“water”),^[2] or otherwise from its same ultimate source, Proto-Indo-European *dʰewbʰ- (“deep, dark, hazy”).^[3] See Dover.
From Proto-Indo-European *teh₂- (“to flow, to melt”), found in hydronyms. This could correspond to the Umbrian counterpart Tifernum Tiberinum with the eastern Italic sound shift bh > f.^[4]

More at Tiber.

Tiberis m sg (genitive Tiberis); third declension

Third-declension noun (i-stem, accusative singular in -im or -in, ablative singular in -ī), singular only.

“Tiberis”, in Charlton T. Lewis and Charles Short (1879) A Latin Dictionary, Oxford: Clarendon Press
Tiberis in Gaffiot, Félix (1934) Dictionnaire illustré latin-français, Hachette.

^ The Latin Dialect of the Ager Faliscus: 150 Years of Scholarship, vol 1 (2009), p.73
^ Douglas Harper (2001–2024) “Tiber”, in Online Etymology Dictionary.
^ G. Alessio "Problemi storico-linguistici messapici" in Studi Salentini12 1962 p. 304.
^ TI: Pellegrini, G.B., Toponomastica italiana, Milano, Hoepli, 1990.