A verb appearing in the Namárië poem, where Tolkien translated it as “tremble” (LotR/377). It is clear form his writings elsewhere that this a poetic rendering, and the actual meaning of the word is “twinkle, give tremulous light” (PE17/66) or “sparkle, glitter” (RGEO/61). It seems to be a combination of the roots √TIN “sparkle” and √THIL “shine silver” (PE17/66), and so is especially appropriate for describing starlight.
Conceptual Development: In The Etymologies from the 1930s, there was a similar verb ᴹQ. tintina- “to sparkle”, likely a reduplication of the root ᴹ√TIN “sparkle”. For Neo-Quenya writing, it is probably preferable to use the better known tintila-.
tintila- vb. "twinkle", present (or maybe rather aorist) pl. tintilar (Nam, RGEO:67)