The plain lying to the south of Angband, later named Anfauglith after it was desolated by the forces of Morgoth. The name was translated “Green Region” (WJ/113). Its second element galen is clearly the lenited form of calen “green”, and its initial element might be some variation of gardh “region” (in early writings, N. ardh).
Conceptual Development: In Silmarillion drafts from the 1930s, this region was named Bladorion of unclear meaning (LR/117); though it may be related to G. bladwen “plain”. In Silmarillion revisions from the 1950s-60s, it was renamed Ard-galen (WJ/113).
ardh (“realm, region”) + calen (“green”)