Malvegil's name probably means "Sword of Gold" or "Golden Sword", being a combination of the Sindarin words mall- meaning "gold", and megil (becoming lenited to vegil) meaning "sword".
Sindarin
malvegil
masculine name. ?Sword of Gold
Elements
Word Gloss malt “gold, gold (as metal)” megil “sword, longsword”
Malvegil
Malvegil
The 6th king of king of Arthedain (LotR/1038), perhaps a combination of malt “gold” and the lenited form of megil “sword”.