ᡤᠣᠯᠮᡳᠨ (golmin, “long”) + ᡥᡝᠴᡝᠨ (hecen, “city wall”), calque of Chinese 長城 / 长城 (Chángchéng).
ᡤᠣᠯᠮᡳᠨᡥᡝᠴᡝᠨ • (golmin hecen)