The roots √UMU and variant √UGU were often assigned a negative sense, either as elaborations on the base root negative √Ū or sometimes (especially in the case of √UGU) serving as its source. The earliest iteration of these more elaborate negative roots was ᴱ√UMU or ᴱ√UVU in the Qenya Lexicon of the 1910s with derivatives like the negative verb ᴱQ. um- or ᴱQ. uv- as well as ᴱQ. ūvanimo “monster” (QL/98); ᴱQ. munta “nothing” from the Qenya Grammar of the 1920s was probably related (PE14/48, 81).
The Etymologies of the 1930s had negative stems ᴹ√UMU and ᴹ√UGU with derivatives like the negative verb ᴹQ. um- as well as ᴹQ. úmea “evil” (Ety/UGU; UMU). This document also had inverted forms ᴹ√MŪ and ᴹ√GŪ, the latter the basis for the negative prefix ᴹQ. ú- with a bad or evil connotation (Ety/GŪ; MŪ). Finally both √UMU and √UGU were mentioned a number of times in later writings in connection to negation (PE17/143, 172; VT49/29). See the entry on negative √Ū and the entry on Quenya negation for further information.