This Elvish root was connected to the sense “two” or “both” throughout Tolkien’s life. The first clear manifestation of this root was ᴱQ. yú “twice” and ᴱQ. yúyo “two” from the Early Qenya Grammar of the 1920s (PE14/49-51, 82-84). The root ᴹ√YŪ “two, both” appeared in The Etymologies of the 1930s with derivatives like ᴹQ. yúyo “both” and ᴹQ. yúkale/N. uial “twilight” (Ety/KAL, YŪ). The root √YU appeared several times in Tolkien’s later writings, generally with the sense “both” (PE17/70; PE21/74; VT48/8, 10). It was likely related to the ancient dual suffix ✶-ū.
Primitive elvish
yul
root. drink
yuldā
noun. what is drunk, a draught
yulmā
noun. drinking-vessel
yulmē
noun. drinking, carousal
yu
root. both, both, [ᴹ√] two
yŭ
conjunction. both
yol/yul
root. smoulder
gō
preposition. from
ăwă
preposition. from
ʒō
preposition. from
A root meaning “drink” in Tolkien’s later writings, most notably the basis for Q. yulda “draught” and Q. yulma “cup” from the Q. Namárië poem (LotR/377). It seems likely the root was coined in association with this poem, though there are no signs of any yul- forms in its earliest drafts from the 1940s (TI/284). The root √YUL (or √JULU) was mentioned a number of times in Tolkien’s later writings in the 1950s and 60s (PE17/63, 180; PE22/155; WJ/416), but there is no sign of it before then. In earlier writings Tolkien generally used √SOK or √SUK for “drink”, and the root √SOK appeared as late as the Quendi and Eldar essay of 1959-60 (VT39/11), an essay that also referenced √YUL (WJ/416). Thus it isn’t clear whether √SOK was supplanted by √YUL, or if the two roots coexisted.