Another name of Dimrost, translated “Shuddering Water” (S/220), a combination of nen “water” and girith “shuddering” (SA/nen, girith).
Conceptual Development: This name was already N. Nen Girith in Silmarillion drafts from the 1930s (SM/130, 313; LR/140).
This is a noun form of gir- “shudder”, most notably an element in names like Nen Girith “Shuddering Water” (S/220; WJ/151) and Girithron “December, ✱Shuddering-one” (LotR/1110; PM/136). In The Etymologies of the 1930s N. girith was glossed “shuddering, horror” under the root ᴹ√GIR “quiver, shudder” (Ety/GIR).