√IBI root. “*cliff, sheer descent”
A root introduced in 1967 notes to explain Q. imbë “valley”. Tolkien said this word was usually perceived as being related to √IMI “in, within” but then he speculated that “It is possibly from a similar but different stem √IBI, and to be compared with S îf (< *īb-), a cliff, a sheer descent” (PE17/92). A possible precursor to this root was ᴹ√IMBE “dell, deep vale” from The Etymologies of the 1930s which was likewise the basis for ᴹQ. imbe/N. imm of the same meaning (EtyAC/IMBE). Tolkien did not explicitly connect this 1930s root to ᴹ√MĪ/IMI, so it may, like later √IBI, have been of independent origin.
References ✧ PE17/92, 155