Welsh derw

← Proto-Brythonic *dar (inherited)

← Proto-Celtic *daru (inherited)

← Ancient Greek δόρυ (cognate)

← Proto-Indo-European *dóru (inherited)

→ English tar (cognate)

→ English durmast oak (mention)

→ Welsh cefnder (affix)

→ Welsh cyfnither (affix)

→ Welsh derwydd (cognate)