Standardised Welsh Place-names list
Notes
The English form of this name is Dunvant. In Welsh, two forms are used: Dyfnant and Dynfant. Although Dynfant is the recommended form in the standard reference book, Rhestr o Enwau Lleoedd/A Gazetteer of Welsh Place-Names (University of Wales Press, 1967), Dyfnant is now the most commonly used Welsh form locally.
However, Dynfant is also a standard form that can still be used and it would be misleading to consider it as a form which has developed under the influence of English. Indeed, there is reason to believe that the English form, Dunvant, evolved from the Welsh form, Dynfant.
Dynfant is an interesting example of the common practice in spoken Welsh of exchanging the consonants fn with nf. Similar historic examples of Dyfnant becoming Dynfant can be found throughout south-west Wales, in Aberdynfant (Llanddeusant, Carmarthenshire), Cwmdynfant (Tirabad, Breconshire) and Craig Dynfant (Cwmteuddwr, Radnorshire), for example. These consonant exchanges also occur in other place-names such as Llyfni > Llynfi (Breconshire) or Llyfnell > Llynfell (Glamorgan). The historical evidence suggests that Dynfant was the usual spoken form in Welsh in the 19th century and at least a part of the 20th century, and it is still used by some people today.
