Origin of the Name "River Thames": Celtic, Latin, or Old English?

Three leading theories for "Thames" (pronounced "temz"):

1. Celtic *Tamesis*: "Dark water" or "dark flow"—referring to its color or tidal nature.
2. Latin *Tamesis*: Roman adoption of the Celtic name; later interpreted as "quiet river."
3. Old English *Temese*: "River boundary"—marking territorial limits.

Most linguists favor the Celtic origin, consistent with other British river names (Avon, Exe, Trent). The spelling "Thames" (with 'h') is a Renaissance affectation mimicking Greek.