Old Irish Fergus

← Proto-Celtic *Wirogustus (derived)

← Proto-Celtic *gustus (derived)

← Proto-Indo-European *ǵews- (root)

← Proto-Indo-European *ǵéwstus (derived)

← Old Irish fer (compound)

← Old Irish guss (compound)

→ Irish Fearghas (inherited)

→ Scottish Gaelic Fearghas (inherited)

→ Icelandic Dufgus (link)

→ Old Norse Dufgus (link)