For most of Tolkien’s life, the Primitive Elvish root for “mother” was √AM. This began with the Qenya Lexicon of the 1910s, where Tolkien gave the root as ᴱ√AMA (QL/30). In The Etymologies of the 1930s it was ᴹ√AM with derivatives ᴹQ. amil and (archaic) N. emil “mother” (Ety/AM¹). In Quenya prayers of the 1950s, the word for mother was Q. Amille. In the last few years of his life, however, Tolkien toyed with the notion of changing this root to √EM. In notes associated with Eldarinwe Leperi are Notessi written in the late 1960s, Tolkien first gave the root as am, but then wrote em next to it with a question mark, along with several new em-derivatives (VT48/19 note #16). The Q. affectionate word emme for “mommy” appeared in the main article, indicating Tolkien did, in fact, adopt this new root, at least for some period of time.
Neo-Eldarin: For purposes of Neo-Quenya writing, I personally prefer to ignore this late change to the root for “mother” and stick with the √AM-forms Tolkien used for most of his life. However, the √AM-forms were less stable in the Sindarin branch of the languages, so I’d use √EM-forms like S. emel and emig, and would assume √AM and √EM were variants of the root, as they were on VT48/19 (see above).
This root was the basis for Q. parma “book”, but Tolkien vacillated on the exact sense for the root. It first appeared as unglossed ᴱ√PARA in the Qenya Lexicon of the 1910s with a single derivative: ᴱQ. parma “skin, bark; parchment; †book, writings” (QL/72). In the contemporaneous Gnomish Lexicon, words like G. padhwen “bark” and G. paglos “parchment” are probably related, along with deleted word G. pand “bark; book” (GL/63). These Gnomish forms hint that the early root was probably actually PAŘA [PAÐA]. Another set of words appearing in the same part of the Gnomish Lexicon and thus probably also related are: G. past “skin”, G. pasta- “skin, peel, flay” and G. path “peel, skin of fruit, fine bark (paper)” (GL/63).
The root ᴹ√PAR reappeared in The Etymologies of the 1930s with a completely different meaning “compose, put together”, though still with the derivative ᴹQ. parma/N. parf “book” along with ON. partha- “arrange, compose” (Ety/PAR). The root ᴹ√PAR “compose, arrange” also appeared in the first version of the Tengwesta Qenderinwa (TQ1) also from the 1930s, again as the basis for ᴹQ. parma “book” (PE18/51). The root √PAR¹ “arrange” > Q. parma “writing, composition, book” appeared again in the second version of the Tengwesta Qenderinwa (TQ2) from around 1950 (PE18/101).
In notes from around 1959 Tolkien reverted to the earlier meaning of the root. In etymological notes from 1959 Tolkien wrote “√PAR-, peel (hence bark, book). [S.] paran, Q. parne, bald, bare” (PE17/171). In a list of Sindarin words from the same period he wrote:
> S paran, naked, bare. Cf. Dol Baran. √PAR “peel”. Cf. Q parna, bare. (Q parma, peel, applied to bark or skin, hence “book”). Q. parca, naked, of persons. S parch (PE17/86).
In another note from this period he gave a very similar derivation with √PAR > Q. parma = [originally] “bark” [later] “parchment, book” noting that the first Elvish writing materials were bark, but he then rejected this etymology (PE17/171).
In notes from the 1960s Tolkien gave:
> √PAR- “learn, to acquire information, not by experience or observation, but by communication”, by the instruction, or accounts of others in words or writing: parma, a book (or written document of some size). To read a book in Elvish was often expressed so: paranye (apārien) parmanen, I am learning (have learnt) by means of a book (PE17/180).
This last meaning of the root is further supported by the phrase Q. cuita’r parë “live and learn” from Late Notes on Verbs composed in 1969 (PE22/154).
Thus the semantic evolution of root seems to be 1910s “✱peel” >> 1930s-1950 “arrange, compose” >> 1959 “peel” >> 1960s “learn”.
Neo-Eldarin: Tolkien’s shifting definitions of the root √PAR make it tricky to use in the context of Neo-Eldarin. While it was the source of Q. parma “book” for all of Tolkien’s life, the exact mechanism of how √PAR was connected to “book” underwent a number of changes. Of these, I think the use of √PAR = “peel” is the one that can be most easily discarded. While this does leave S. paran “bare” from the name S. Dol Baran with no etymology, that word might be salvaged by assuming it was derived instead of an unrelated (hypothetical) root ✱√PARAN.
The other two meanings of the root, “compose” (1930s-1950) and “learn” (1960s) are both popular parts of Neo-Eldarin. The verb Q. par- has become the basis verb for “learn” verbs in Neo-Eldarin since its publication in PE17 in 2007. However, the sense “compose, arrange” is also well established. I think it is best to assume this root means both “compose, put together” in general as well as “compose (information)” = “learn”, to retain both these senses. As for “arrange”, that seems to be better covered by √PAN.