The first appearance of this root was as unglossed {ᴱ√WORI >>} ᴱ√GWORI in the Qenya Lexicon of the 1910s with derivatives like ᴱQ. ’wōre and G. gur “sweet” (QL/104); the latter appeared as gûri in the contemporaneous Gnomish Lexicon (GL/43). These early words were elements in ᴱQ. miruvóre and its Gnomish equivalent G. gurmir (QL/61; GL/43).
The root √WOR reappeared in Words, Phrases and Passages in the Lord of the Rings from the late 1950s, with the gloss “express, cause to exude (by pressure)”, again as the basis for the second element of Q. miruvórë: ✶wōri “juice (esp. of fruit)” (PE17/37-38). But Tolkien went on to say “This is false etymology. High Elvish. There was not in fact any word wor- in Elvish, Quenya or Sindarin.” He then concocted a new etymology for miruvórë as a loan word from Valarin mirubhōze (PE17/38). This Valarin origin of the word was repeated in the Quendi and Eldar essay of 1959-60 (WJ/399). In notes from 1967 Tolkien admitted that the actual inspiration of the word was Germanic među “mead” + wōþi “sweet” (PE17/65).
This root was the basis for the prefix Q. o- and S. go- “together”. In the 1910s Gnomish Lexicon, G. go- (unaccented) or gwa- “together” was derived from primitive ᴱ✶ŋu̯a and the Qenya form was ᴱQ. ma- (GL/40-41). In the 1920s the Early Noldorin form was still ᴱN. go- or gwa- but the Qenya form was ᴱQ. va- (PE13/162), probably from primitive ✱wa-. In The Etymologies of the 1930s Tolkien gave the root as ᴹ√WŌ̆ “together” with derivatives ᴹQ. o- and N. go- or stressed gwa- (Ety/WŌ; EtyAC/WŌ).
In The Etymologies Tolkien explained the go-/gwa- variation in Noldorin as the result of the sound change whereby stressed wŏ became wa in Common Eldarin (Ety/WŌ); Tolkien gave a similar explanation for Sindarin in the Quendi and Eldar essay of 1959-60 (WJ/367). Despite stressed wŏ > wa being an ancient change, the wa variant did not survive in Quenya. Tolkien explained the sound change whereby wo became o in Quenya several times: in the Outline of Phonetic Development (OP1) from the 1930s, in the Outline of Phonology (OP2) from the early 1950s, and in the Quendi and Eldar essay of 1959-60 (PE19/53, 106; WJ/367). The root √WO itself also appeared several times in Tolkien’s later writings (PE17/16, 191; WJ/361), in one place with the variant √WONO (PE17/191).