A pass between Himring and Dorthonion (S/123). This name seems to be a compound of (N.) agor “narrow” and lond “strait, pass” (Ety/AK, LOND). This name sometimes appeared as Aglond, probably an older form of the name (WJ/338, Ety/AK).
Conceptual Development: The name ᴱN. Aglon first appeared in the Lays of Beleriand from the 1920s (LB/227) and N. Aglon was used in Silmarillion drafts from the 1930s (LR/127, 265). In The Etymologies, it was translated as “defile, pass between high walls”, and this was the source of the derivation given above (Ety/AK, LOD).