Proto-Celtic *kʷetwares

→ Breton pevar (inherited)

→ Welsh pedwar (inherited)

→ French Périgueux (mention)

→ Irish ceathair (inherited)

→ Scottish Gaelic ceithir (inherited)

→ Manx kiare (inherited)

→ Cornish peswar (inherited)

→ Latin Petrocorii (derived)

→ Old Irish cethair (inherited)