This word was used for “flour” related words for much of Tolkien’s life. It first appeared as ᴱQ. pole (poli-) “oats” in both the Qenya Lexicon and Poetic and Mythological Words of Eldarissa of the 1910s, derived from the early root ᴱ√POL-I which was, in that document, distinct from ᴱ√POLO “have strength” (QL/75, PME/75). The word reappeared with various glosses in documents from the 1920s: “grain; unground kernels of oats, wheat, etc.” (PE15/73), “grain” (PE14/75), “flour” (PE16/141).
In the Declension of Nouns from the early 1930s it was ᴹQ. pole “flour, meal” (PE21/12), but in The Etymologies of the 1930s it became ᴹQ. pore (pori-) “flour, meal” derived from primitive ᴹ✶pori under the root ᴹ√POR (Ety/POR). Tolkien may have changed l to r to better distinguish it from the root ᴹ√POL(OD) “physically strong” (Ety/POL). In notes from around 1967, however, Tolkien became dissatisfied with the meaning of the root √POL, saying:
> POL. This cannot refer to strength. (Too obvious a reminiscence of [Latin] pollens); also it does not account for poli- “meal, grist”. POL- should have senses “pound up”, break up small, reduced to powder etc. (PE17/181).
Thus it seems he restored pole (poli-). However, in notes from 1968 he reversed himself, saying:
> Q. pol, large, big (strong). polda big. DELETE pole “meal”! Make it mule (PE17/115).
Neo-Quenya: Given the widespread use of √POL in words having to do with physical ability, I agree with Tolkien’s 1968 note that poli- is not viable for “flour” words. I recommend Q. mulë for “meal” = any ground grains in general, but I think it is worth retaining 1930s ᴹQ. pore specifically for “flour”.
[polë (stem poli-) noun "meal, grist" (PE17:115, 181), a word Tolkien decided to replace by mulë; perhaps polë was a variant of porë.]