Old Norse fastr

← Proto-Germanic *fastuz (inherited)

→ Danish fast (derived)

→ Faroese fastur (derived)

→ Westrobothnian fȧst (inherited)

→ Old Swedish faster (inherited)

→ Icelandic fastur (inherited)

→ Norwegian Bokmål fast (derived)

→ Norwegian Nynorsk fast (derived)

→ Swedish fast (inherited)