A word appearing as G. cuilog “alive, lively” in the Gnomish Lexicon of the 1910s, an adjectival form of G. cuil “life” (GL/27). Tolkien specified that this word was “usually metaph[oric]”, so probably “lively” was a better translation than “alive”.

Neo-Sindarin: For purposes of Neo-Sindarin, I’d update this word to ᴺS. cuileb “lively” using the later adjective suffix -eb, but for “alive” I’d use [N.] cuin.