The first element in Rhimdath is related to Noldorin rhib-, rhimp, rhimmo ("to flow like a [?torrent]"), derived from the stem RIP- ("rush, fly, fling"). Christopher Tolkien stated that the name Rhibdath or Rhimdath, given the meaning "Rushdown", was a hastily scribbled addition at the end of the R-stems. In the index he noted that this name only appeared in the Etymologies but is the river described above.[note 1] As the stem DAT- is glossed as "fall down", it is possible that the second element in Rhimdath is a derivative of this stem.
Noldorin
rhimdad
place name. Rushdown
Elements
Word Gloss rhib- “to flow like a (?torrent)” dad “down” Variations
- Rhibdath ✧ Ety/RIP; TII/Rushdown
- Rhimdath ✧ Ety/RIP; RS/205; RSI/Rhimdath; TII/Rushdown
Rhimdath
Rhimdath
A river on the other side of the Misty Mountains from the river Hoarwell (S. Mitheithel). It appeared in The Etymologies as N. Rhimdath < Rhibdath (Ety/RIP), and also appeared as Rhimdath on a very early map of the wilderlands (RS/205). In a later draft map it was labeled Rhimdad (TI/296), but was unlabeled in the maps published in The Lord of the Rings.
According to The Etymologies, its initial element is derived from N. rhib- “to flow like a (?torrent)”, apparently assimilated to Rhim-. Its final element is most likely N. dad “down”. Roman Rausch suggested (EE/1.5) that its earlier form Rhimdath may instead have N. dath as its second element, perhaps with the meaning “steep fall, abyss” (EtyAC/DAT).
If this name was adapted to the phonology of later Sindarin, it might be S. ✱Rimdad.