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).
Theoretical initial element in ancient wādelo “those who departed Middle-earth”, but according to Tolkien this was a false etymology (WJ/364).