Proto-Germanic *þrawō

→ English threap (derived)

→ English threpe (derived)

→ Old English þrea (inherited)

→ Old English þreapian (derived)

→ Icelandic þrá (inherited)

→ Old Norse þrá (inherited)

→ Norn attrå (derived(nrn/da))

→ Norn trå (derived)

→ Swedish trå (derived)