Langon's race and the meaning of his name are unknown. During the Elder Days he became a servant of Melko.
When the Gods went to the Great Lands to attack Melko, he ran north and locked himself in Utumna. Then the Valar opened the gates and asked him to come forth. However, Melko sent Langon to negotiate with their enemies. His message was full of insolence and false flattery, causing wrath among the Gods.
Although Langon is never glossed, in the Gnomish Lexicon there are two entries that could be related: lang ("to blare, clang, ring"), langon ("great bell"). So perhaps the name has something to do with Langon "blaring forth" Melko's message.