An unglossed root in The Etymologies of the 1930s with no derivatives of its own but two extended roots ᴹ√MISIK and ᴹ√MISID; probably the sense of the base root was “✱wet” (EtyAC/MIZD). It was also Tolkien’s intent that this ᴹ√MIS² be the basis for ᴹ√MITH “✱grey, mist” by way of blending with ᴹ√KHITH “mist, fog” (EtyAC/MITH). Extended ᴹ√MISIK or ᴹ√MISK had derivatives ᴹQ. miksa/N. mesg “wet” (Ety/MISK) and extended ᴹ√MISID or ᴹ√MIZD had various different meanings in derived languages: ᴹQ. miste “fine rain” vs. N. mîdh “dew” vs. Dor. mîd “moisture” (Ety/MIZD). The root ᴹ√MIZDI also appeared in both the first and second versions of Tengwesta Qenderinwa from the 1930s (TQ1: PE18/43) and around 1950 (TQ2: PE18/93).
Note that in the Qenya Lexicon of the 1910s there was a root ᴱ√MISI “mingere [Latin = urinate]” with a derivative ᴱQ. mis “urine” (QL/62); this might have been a precursor to 1930s ᴹ√MIS² “✱wet”.
A root in The Etymologies of the 1930s glossed “go free, stray, wander”, with derivatives like ᴹQ. mista-/N. mista- “stray (about)”, ᴹQ. mirima “free” and N. mist “error, wandering” (Ety/MIS). It was originally just glossed “free” (EtyAC/MIS).