Cabed Naeramarth was the river chasm known in earlier times as Cabed-en-Aras, the "Deer's Leap", because it was narrow enough for a deer to leap from cliff to cliff across the River Teiglin that flowed below. It was here that Túrin crossed the river and succeeded in slaying the dragon Glaurung, but while he lay insensible after that feat, his wife Níniel learned from the dying monster that she was Túrin's own sister Nienor. In dismay at this dreadful news, she cast herself into the chasm and was carried away by the river, and so the ravine gained its new name of Cabed Naeramarth, the "Leap of Dreadful Doom".
Cabed Naeramarth translates to "Leap of Dreadful Doom". amarth = doom.