Ambarussa

Ambarussa (Q, pron. [ˌambaˈrusːa]) was Nerdanel's mother-name for her twin sons Amrod and Amras. It translates as "top-russet", referring to the color of their hair. After Fëanor their father insisted on giving them each seperate names Nerdanel named Amras Umbarto, the fated, and Fëanor changed it to Ambarto. But the twins each still called the other Ambarussa.

References

• The Peoples of Middle-earth, The Shibboleth of Feanor