@@@ Language unknown and apparently never defined. In notes from the 1950s, Tolkien said it was “Another name from prim[itive] FG [Fall of Gondolin] - meaningless then and now. But it was not intended to have any meaning in Q[uenya] or S[indarin]” (WJ/320).
Sindarin
galvorn
noun. a black metal devised by the dark elf Eol
galvorn
noun. type of dark metal devised by Eöl, *(lit.) shining-black
rodëol
proper name. metal of Eöl
Name of the black metal devised by Eöl as mentioned in The Silmarillion (S/133), apparently a combination of √GAL “shine” and morn “black”.
Conceptual Development: In Silmarillion drafts from the 1950s Tolkien first gave this name as Rodëol “metal of Eöl” (WJ/322), where the initial element seems to be a later iteration of N. rhaud “metal” from The Etymologies of the 1930s (Ety/RAUTĀ). Tolkien then considered a number of alternate names for the metal, all various forms of the name of Eöl’s son Maeglin, since at this stage he intended the son to be named after the metal (WJ/48, 322). Later Tolkien decided that “the metal must not have same name as Maeglin”, and he settled on galvorn for the metal, as discussed above.