The article deals with the ancient name of the longest river solely in England, the Trent, flowing past Stoke-on-Trent and Nottingham to the north Sea. In a passage that has raised debate and led to a number of misinterpretations in literature, Tacitus recorded it as (emended) Trisantona, which has been explained from Old Irish set 'course' and Welsh hynt 'path' as 'trespasser, one that overflows' (of a stream liable to flood). Trisantona or the like would be the name of other rivers, including the Tarrant in Dorset and Tarannon or Trannon in mid-Wales. Yet the interpretation 'trespasser' has grave phonetic and semantic defects. They are removed by a new etymology on the basis of old Irish set 'treasure' (Modern Irish seoid) and Welsh chwant 'desire' from hypothetical Common Celtic *suanto-. The paper provides textual, historical and linguistic arguments supporting this etymological interpretation. Trisantona or (preferably) reconstructed *Trisuantona (from *Tresuantona) would thus (instead of 'trespasser, flooder') mean 'she of great desire, she who is much loved.' The implication is that the trent (like the English rivers Dee 'goddess' or Brent 'she who is exalted') was regarded as a celtic female deity, a passionate and perhaps dangerous entity.