Welsh castell

← Breton kastell (cognate)

← Breton kestell (mention)

← Proto-Brythonic *kastell (inherited)

← Cornish kastel (cognate)

← Latin castellum (derived)

← Middle Welsh castell (inherited)

→ English castle (cognate)

→ Breton kastell (cognate)

→ Welsh cas (mention)

→ Welsh Castell-nedd (compound)