A root in The Etymologies of the 1930s glossed “swallow” with variant ᴹ√LANK and derivatives ᴹQ. lanko/N. lhanc “throat” (Ety/LAK¹, LANK), the latter an element in N. tarlanc “stiff-necked, obstinate” (Ety/TÁRAG). This last word was changed to S. tarlang in Tolkien’s later writings (PE17/92; RC/536), consistent with an earlier but rejected form ᴹ√LANG for ᴹ√LANK in The Etymologies (Ety/LANK).
In later writings, Q. lango/S. lang meant “neck” rather than “throat”, so it is tempting to retain ᴹ√LAK for “throat” and other swallow-words. But it would be very confusing to have such similar but unrelated words for “neck” and “throat”, so I recommend using the root ᴹ√SLUK for “swallow” instead, and Q. lango, S. lang for both “neck” and “throat”.
A root in The Etymologies of the 1930s glossed “night” that (along with ᴹ√DOM) was the basis for the ᴹQ. lóme/N. dû “night” (Ety/DOƷ). It replaced some rejected variants ᴹ√LOƷ and ᴹ√DAW (EtyAC/LOƷ). Many of the derivatives of ᴹ√DOƷ were later assigned to other roots: N. dûr “dark” became S. dûr “dark” < √NDU “under, down” in notes from the late 1950s or early 1960s (PE17/152) and ᴹQ. lóna “dark” became Q. lúna (PE17/22). There are no signs of ᴹQ. ló “night” and N. daw “night-time, gloom” in Tolkien’s later writing. Future derivations of Q. lómë/S. dû only mention the root √DOM (PE17/152; PE22/153) and thus ᴹ√DOƷ may have been abandoned.
In a message to the Elfling mailing list from July 2012 (Elfling/362.96), David Salo suggested there might be a later root ✱√DU serving as the basis for Q. lúna “dark” and Q. lúmë “darkness”, though the latter might instead be from √LUM. Such a root ✱√DU is not attested in Tolkien writings, but if it existed, it could be a later iteration of ᴹ√DOƷ. Another possible example of the root ✱√DU is primitive ✶durnŭ “dark of hue”.