An island in the river Adurant translated “Green Isle” (S/123), a combination of tol(l) “island” and the lenited form of calen “green” (SA/tol, calen).
Conceptual Development: The name N. Tol-galen also appeared in Silmarillion drafts from the 1930s (LR/305) and at one point in Lord of the Rings drafts from the 1940s was considered as name for Tol Brandir (TI/271).
toll (“island”) + calen (“green”)