Malbeth's name is Sindarin for "Golden Word" from mal meaning "gold", and peth (becoming lenited to beth) meaning "word, voice".
Sindarin
malbeth
masculine name. *Golden Word
Elements
Word Gloss malt “gold, gold (as metal)” peth “word”
Malbeth
Malbeth
Loremaster of Arthedain called “the Seer” who named Arvedui (LotR/781), his name appears to be a combination of malt “gold” and the lenited form of peth “word”.