Breton placename
Celtic toponymy is the study of place names wholly or partially of Celtic origin. These names are found throughout continental Europe, the British Isles, Anatolia and, latterly, through various other parts of the globe not originally occupied by Celts.
The Proto-Indo-European language developed into various daughter languages, including the Proto-Celtic language. In Proto-Celtic ("PC"), the Proto-Indo-European ("PIE") sound *p disappeared, perhaps through an intermediate *ɸ. After that, languages derived from Proto-Celtic changed PC *kw into either *p or *k (see: P-Celtic and Q-Celtic languages). In P-Celtic languages, PC *kw changed into *p. In Q-Celtic dialects it developed into /k/. Modern Celticists believe these changes happened after the split between Insular Celtic languages and the Continental Celtic languages.
P-Celtic languages include the Continental Gaulish language and the Brittonic branch of Insular Celtic. Common Brittonic is the ancestor of Welsh, Cornish and Breton.
Ancient Q-Celtic languages include the Continental Celtiberian and the Goidelic branch of Insular Celtic. Goidelic is the ancestor of the Gaelic languages Irish, Scottish Gaelic and Manx.
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