Beware, older languages below! The languages below were invented during Tolkien's earlier period and should be used with caution. Remember to never, ever mix words from different languages!

Gnomish

gaithrin

adjective. like steel

A word appearing as G. gaithrin “like steel” in the Gnomish Lexicon, an adjectival form of the noun G. gais “steel” (GL/37).

Neo-Sindarin: Since I adapt the Gnomish noun as ᴺS. gaes “steel” for purposes of Neo-Sindarin, I would adapt the adjective as ᴺS. gaethren “of steel”, with sr becoming thr.