This was the root for Elvish words meaning “yellow” for much of Tolkien’s life, though with some minor variations. It appeared as ᴱ√MALA “yellow” (usually mali-) in the Qenya Lexicon of the 1910s with derivatives like ᴱQ. malina “yellow” and ᴱQ. malikon “amber” (QL/58). It also appeared in a list of M-roots at the end of that section (QL/63). It had derivatives in the contemporaneous Gnomish Lexicon such as G. malon “yellow” and G. malthos “butter cup” (GL/56).
In The Etymologies of the 1930s it seems Tolkien first gave this root as ᴹ√MAL (EtyAC/MAL) but rejected this and replaced it with ᴹ√SMAL “yellow” (Ety/SMAL). It had derivatives like ᴹQ. malina/N. malen “yellow”, ᴹQ. malta/N. malt “gold (as metal)” and ᴹQ. malo/N. hmâl “pollen, yellow powder” (< ᴹ✶smalu), with some revisions in Noldorin forms as Tolkien vacillated on whether or not primitive sm- resulted in voiceless nasal hm- or a voiced nasal m-.
This √SMAL vs. √MAL variation seems to have continued into Tolkien’s later writings, as seen in Common Eldarin: Noun Structure from the early 1950s where ✶malu >> ✶smalu “dust, grit” (PE21/80), probably a later iteration of ᴹ✶smalu “pollen, yellow powder” from The Etymologies. But it seems Tolkien settled on √MAL as evidenced by the extended root √MALAT “gold” from The Shibboleth of Fëanor from 1968 (PM/366).
Tolkien’s Elvish words for “gold” were fairly stable in his conception of the languages, resembling Q. laurë and S. glaur for most of his life. The main exception was the Early Noldorin and Gnomish forms of the 1910s and 20s, which were ᴱN./G. glôr (PE13/144; GL/40). These early forms survived to some degree in Tolkien’s later conceptions, because in Sindarin compounds au often reduced to o, and thus the name Glorfindel “Golden-hair” retained the same form and meaning for Tolkien’s entire life despite the revision of G. glôr >> S. glaur.
Tolkien’s first primitive root for these words was ᴱ√LOU̯RI in the Qenya Lexicon of the 1910s (QL/51). This reflected the Early Qenya sound change whereby [[eq|[ei], [ou] became [ai], [au]]]; later on these ancient diphthongs usually became [ī], [ū]. In this earliest conception, the root and its derivatives referred to the physical substance of “gold”, though not quite its mundane nature: Tolkien said that ᴱQ. laure was the “mystical” or “magic” name of gold as opposed to its more mundane name ᴱQ. kulu (QL/42; LT1/100).
Tolkien introduced a new root ᴹ√GLAWAR or ᴹ√LAWAR for these words in The Etymologies of the 1930s, along with the modified form for its Noldorin derivative N. glaur (Ety/GLAW(-R), LÁWAR). Tolkien said that ᴹ✶laurē referred to the “light of the golden tree Laurelin” (Ety/LÁWAR), indicating a conceptual shift in the meaning of the root to “golden light or colour” rather than “mystical gold”. Indeed, in etymological notes Tolkien wrote sometime around 1960, Tolkien said of √LAWAR: “The application to gold of this stem was poetic and referred to colour primarily ... not to material (malta)” (PE17/159).
Tolkien’s representation of this root as both √GLAWAR and √LAWAR indicates some uncertainty on whether the initial gl- was from Common Eldarin or was only a later Ancient Telerin innovation. However, in later writings Tolkien typically represented the primitive word as ✶glawar(e) (PE17/17; PE21/80; VT41/10), and in the Outline of Phonology from the early 1950s Tolkien gave the Ancient Quenya word AQ. alaurē “sheen of gold” whose vowel augment arose from an abnormal vocalization of the ancient spirantalized initial g-: ✱glawarē > glaurē > ʒlaurē > alaurē (PE19/79). This strongly indicates the primitive root was √GLAWAR.