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 1940s, 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).
This root is the basis for Elvish question words. When it first appeared in the Gnomish Lexicon of the 1910s, Tolkien said ᴱ√MA was the “root of indef[inites]” (GL/55), and it served as the basis for the indefinitive suffix G. -(u)m and ᴱQ. -(u)ma (GL/55; PE14/42, 71). In the Gnomish Lexicon, question words were derived from the root ᴱ√DO instead: G. don “who”, G. dos “when”, G. dui “where”, etc. (GL/30). There are no signs of interrogative ᴱ√DO in Tolkien’s later writings, but indefinite -(u)ma survived until at least the late 1940s (PE23/99, 105).
By the time Tolkien wrote the ᴱQ. Oilima Markirya poem around 1930, Quenya question words also generally began with ma-: ᴱQ. man kiluva kirya ninqe? “Who shall see a white ship?” (MC/213). This remained true thereafter, and the same seems to be true of Sindarin as well, though we have far fewer examples: S. man agorech?, untranslated but apparently: “✱and said Rían to Tuor: what have we done?” (VT50/5). The “interrogative base” √MA is mentioned in Quenya Notes from 1957 (QN: PE17/162) and again in notes from around 1968 (VT47/19).
√MA was not completely divorced from indefinites in Tolkien’s later writings, however, given late 1940s indefinite suffix -(u)ma (PE23/99, 105) and his use of Q. ma for an indefinite neuter pronoun “(some)thing” as opposed to the indefinite personal pronoun Q. mo “(some)one” (PE22/154; VT42/34). The exact relationship of interrogative √MA with these indefinite forms is not entirely clear, however.