ᴱ√TUÐU root. “kindle”
The root ᴱ√TUŘU “kindle” [TUÐU] appeared in the Qenya Lexicon of the 1910s with variant forms ᴱ√TUSO and ᴱ√TUSU as well as derivatives like ᴱQ. tunda- “kindle”, ᴱQ. turu “wood, properly firewood”, and ᴱQ. tusturin “match” (QL/96). The contemporaneous Gnomish Lexicon had a similar primitive form tudh- with derivatives like G. tund “log for the fire”, G. tusta- “inflame, kindle, set light to, burn”, and G. tuthli “match” (GL/72). However, the Gnomish Lexicon also had words like G. drui “wood, forest” and G. duru “wood; a pole, beam, or log” (GL/31). Since initial d- > t- in Early Qenya, it seems likely that ᴱ√TUŘU “kindle” may also represent a blending with an unattested root *ᴱ√DURU “wood”.
Many years later Tolkien gave a hypothetical root √TUD in contrasted to √TUL to illustrate certain principles of etymological variations (VT48/25). It is not clear whether this √TUD is related to earlier ᴱ√TUÐU “kindle”. Nevertheless, I think it is worth positing a Neo-Root ᴺ√TUD “firewood, kindling” to salvage Early Qenya and Gnomish words of similar meaning.
References ✧ GL/72; LT1A/Turuhalmë; QL/96