Bran Vran

Gaulish chieftains from fourth and third century BC have names whose clear etymology is preserved in Serbian. Breton, Welsh, Irish, Lithuanian and Slavic languages are the only ones which share "vran" as a word for raven and crow, but only Serbian, Croatian, Bosnian and Polish languages use Vran, Vron as a word for black. Slavic languages are the only ones which have preserved the old word "Bran" meaning to defend, protect. How is this possible if Slavs and Celts were not supposed to have had any contacts?

http://oldeuropeanculture.blogspot.ie/2014/04/bran-vran.html