Edennil was a Sindarin epithet given by the Eldar to Finrod, meaning "the Friend of Men". Finrod was the Elf who first came upon Men in Beleriand and befriended them.
J.R.R. Tolkien, Christopher Tolkien (ed.), Morgoth's Ring, "Part Four. Athrabeth Finrod ah Andreth: 'The Debate of Finrod and Andreth'"