GWAWR (standardized modern form)
Gwawr, and her supposed sister Nyfain, are listed as daughters of Brychan, king of Brycheiniog, in the earliest (and presumably most reliable) lists of his children. However for all of Brychan's alleged children, even if the individual is historic, the specific relationship may have been invented for later dynastic purposes. Bartrum (WCD) gives the two women an approximate calculated date in the late 5th century (these calculated dates are based on standard generation-lengths from individuals who can be more solidly dated). Both appear in all the early lists of Brychan's children, although in one Nyfain's name is badly (and oddly) corrupted. Gwawr is said to have married Elidir Llydanwyn ap Meirchion Gul, and was the mother of Llywarch Hen. Her citations (Bartrum EWGT) are as follows. (In all of the following discussions, if I have failed to note my immediate source for a manuscript citation, it can be assumed to come from one or the other of Bartrum's works, as listed in the References section.)
Guaur - De Situ Brecheniauc (Cotton ms. Vespasian A xiv, fos. 10v-11v (ca. 1200) text perhaps a century earlier.
Gwawr - Cognacio Brychan (Cotton MS. Domitian I, fox. 157v-158v) ms. dated 1502-55, copied from a ms poss of the 13th c.
Gwawr - JC MS 20 written late 14th c., copied from ms ca. 1200
Gwawr - Plant Brychan
Other early examples of Gwawr as a personal name can be found in genealogical material and other sources, with variable levels of reliability.
There seems no reason not to accept that the personal name is linguistically identical to the common noun gwawr meaning "dawn". Given this, we can reconstruct a late Brittonic *uori- (based on GPC), and a probable Latinized written form Voria. A 5th century date places this before the complete loss of inflectional endings, but after their severe reduction. So the pronunciation might be something like: ['wor-j@]. Or, approximated by English syllables, "WOHR-yeh".