This root first appeared as ᴱ√TYULU “tall” in the Qenya Lexicon of the 1910s with derivatives like ᴱQ. tyulta- “to rear up, stick up”, ᴱQ. tyulma “mast”, and ᴱQ. tyulusse “poplar” (QL/50). The last two words reappeared in The Etymologies of the 1930s under the root ᴹ√TYUL “stand up (straight)” along with a Noldorin derivative N. tulus “poplar-tree” (Ety/TYUL).
In notes from the 1940s and 50s Tolkien gave new primitives forms for one of these words: ᴹ✶kyul(u)mā “mast” (SD/419; PE21/65, 74), indicating a change from ᴹ√TYUL >> ✱ᴹ√KYUL. This was probably in keeping with Tolkien’s decision in the 1950s to remove initial palatalized dentals as a feature of Primitive Elvish; see the entry on how [[at|[j] was lost after initial dentals]] in the Welsh-like branch of the Elvish languages for further details.
Neo-Eldarin: For purposes of Neo-Eldarin, I prefer to ignore Tolkien’s decision to remove initial palatalized dentals from Primitive Elvish. As such, I prefer √TYUL over √KYUL in order to retain attested Noldorin words from the 1930s form of the root.
A root in The Etymologies of the 1930s glossed “fix, indicate, decide” with derivatives like ᴹQ. sanda/N. thann “firm, true, abiding” and ᴹQ. sanye “rule, law” (Ety/STAN; EtyAC/STAN).