Old Norse þerra

← Proto-Germanic *þarzijaną (inherited)

← Proto-Germanic *þersaną (mention)

← Proto-Indo-European *ters- (root)

← Proto-Indo-European *torséyeti (inherited)

← Proto-Indo-European *ters- (mention)

→ Old Norse þorna (link)

→ Old Norse þerrir (link)

→ Albanian ter (cognate)