A proposed alternate name of Glaurung, but the change was rejected (PE17/183). This name is a combination of ang “iron” and ruin “fiery red”.
Sindarin
Angruin
noun. 'Iron Fire'
angruin
masculine name. Iron Fire
Elements
Word Gloss ang “iron” ruin “red flame; fiery red”
prop. n. 'Iron Fire'. Tolkien notes "Alter Glaurung > Angruin".