A noun in The Etymologies of the late 1930s glossed “wool” and derived from the root ᴹ√TOW (Ety/TOW).
Conceptual Development: The Qenya Lexicon and Poetic and Mythological Words of Eldarissa of the 1910s had ᴱQ. oa “wool” under the early root ᴱ√OWO (QL/71). This became ᴱQ. toa in the contemporaneous Gnomish Lexicon, cognate to G. tô “wool” from primitive ᴱ✶tou̯ (GL/71). ᴹQ. tó “wool” first appeared in the Declension of Nouns (DN) from the early 1930s, but there it was an example of a monosyllable ō-noun derived from -ōʒǝ: ✱tōʒǝ (PE21/40). Compare this to ᴱN. tô “wool, fleece” from Early Noldorin Word-lists of the 1920s derived from primitive ᴱ✶togō or ᴱ✶togo (PE13/154, 165).
Possible Etymology: The derivation ᴹ√TOW > ᴹQ. tó in The Etymologies seems to be the result of a sound change whereby stressed ou became ō (vs. unstressed ou becoming ū); this change was mentioned in both the Outline of Phonetic Development (OP1) from the 1930s (PE19/53) and the Outline of Phonology (OP2) from the early 1950s (PE19/106). However, in Tolkien’s later writing, the usual development of ou was to ū even if the syllable was stressed: compare ✶lou > lū and ✶lounē̆ > lūn in notes from the late 1960s (PE17/137).
Neo-Quenya: I would retain tó “wool” for purposes of Neo-Quenya, but would assume it is derived from either ✱tō or ✱togō, similar to its derivation from the earlier 1930s. This also makes it easier to retain ᴱN. tô “wool” for purposes of Neo-Sindarin.
A noun in The Etymologies of the 1930s glossed “muscle, sinew; vigour, physical strength” derived from primitive ᴹ✶tūgu under the root ᴹ√TUG (Ety/TUG). This root also had an adjective ᴹQ. tunga “taut, tight; resonant (of strings)”, clearly referring to the use of sinew in making stringed instruments. Thus I think tuo likely refers mainly to “muscle, sinew”, and only metaphorically to “vigour, physical strength”, as in: tana Elda same tuo “that Elf has muscle = has physical strength”.