Pryderi

The name 'Pryderi' arises in each of the four branches of the Mabinogi, and is the factor which unites these legends.
The legends known as “The Four Branches of the Mabinogi” had their origins in the west of Ireland, in the environs of the royal place called ‘Regia Altera’ in Ptolemy’s map of Hibernia. Taken to Wales in the last quarter of the 12th century, they were redacted and translated to Welsh. Many of the original names of people and places were retained, but were written phonetically in Middle Welsh. One such name is ‘Pryderi’.
An Irish speaker, hearing the sound ‘Pryderi’ would think: “chief from the stern”, or “principal from the behind” or “first/prime from the buttocks” – the Irish words which would have come to his mind being “prímh-dheiridh”. In this compound word ‘mh’ is frequently silent in western and northern gaelic dialects, and the final ‘dh’ is nowhere pronounced, so that the listener only hears ‘prí-dheiri’, scribed phonetically as ‘Pryderi’ in Middle Welsh versions of these legends.
As to the meaning “first from the buttocks”, Pryderi was the first-born child of Pwyll and Rhiannon.
As to correct pronunciation of Pryderi, 'pree-jerry' is as close to perfection as ought be expected.
Note: See 'príomh' and 'deire' in any Irish-English dictionary.

The meaning of Pryderi in Welsh is - to worry.