Erbium is named after the swedish find spot Ytterby, just like Yttrium, Terbium and Ytterbium. Apparently the chemists of that time were not very creative in naming.

Therefore Erby is the third monster of the Ytterbies.

Yttrium is always grouped with other rare earth elements. It was discovered in the small place of Ytterby in Sweden, which it is named after.

Yttri the monster is the smallest of the Ytterbie family.