An unglossed root ᴱ√MṆGṆ appeared in the Qenya Lexicon of the 1910s with derivatives ᴱQ. mange “grease” and ᴱQ. manya “butter” (QL/62). G. mang “butter” from the contemporaneous Gnomish Lexicon is also almost certainly related (GL/56). In Qenya Word-lists from the 1920s Tolkien gave ᴱQ. mingwe “butter” which may be related (PE16/141).
Neo-Eldarin: For purposes of Neo-Eldarin, I think it is worth positing a root ᴺ√MANGYA to salvage early “butter” words.
The primitive form ᴱ✶mḷgo appeared in Early Noldorin word lists of the 1920s serving as the basis for various “oil” words (PE13/139). It may have replaced ᴱ√ILI “shine oily” from the Qenya Lexicon of the 1910s (QL/42), and may in turn have been replaced by √LIP “oil” from a list of roots from 1968 (VT44/15), though in this list √LIP had no derivatives.
Neo-Eldarin: For purposes of Neo-Eldarin, I think it is worth positing a Neo-Eldarin root √MILIG to salvage derivatives of 1920s ᴱ✶mḷgo.