Anach

The initial an- in this name is possibly 'long', but -ach is less clear. It is perhaps connected to achad, 'neck', but in a geographical sense that word usually meant a ridge rather than a pass or valley. Another possibility is the old word acha, which would make Anach the 'long waterfall'. That alternative certainly fits the geography, but the word acha is not attested in any but Tolkien's earliest writings.

A quite different interpretation might connect the name with the Elvish root ának-, meaning 'bite', which doesn't at first sight seem directly relevant, but might conceivably have been used to describe a valley cut out of the surrounding mountainous lands.

Finally there is a potential connection to the Elvish root ak-, describing a feature that is narrow or confined. On this interpretation, then, Anach would mean 'long and narrow'. One indirect hint towards this would be from the Pass of Aglon at the other end of Ered Gorgoroth, which is known to originate from ak-. On this translation, then, Anach would therefore be partially cognate with the nearby Pass of Aglon.