A semi-nonsensical 'nordic sounding' language that the inventor has dubbed "Yulish", but is referred to in the script and novelisations as "Elvish"
Elvish was developed by David J. Peterson, a renowned language creator in the world of TV and film. His most notable work was creating Dothraki and High Valyrian for the hit HBO series, Game of Thrones. Peterson also made languages featured in The 100, Penny Dreadful, The Witcher, and Lovecraft Country in addition to movies like Thor: The Dark World, Doctor Strange, and Bright. Peterson's expert language creation skills will soon be on display in Denis Villeneuve's Dune, set to release in 2021.
Despite the fact that The Christmas Chronicles classified the language as "Elvish," Peterson considered it to be "Yulish." He invented it to be the official language spoken by Santa Claus and the large number of Christmas elves that resided in the North Pole. Yulish purposely used a nonpast tense and the main stress in the pronunciation featured a dip in the pitch. The elves, of course, had higher-pitched voices based on their size. If The Christmas Chronicles 2 hits the same level of popularity as the original movie, the elves will certainly be back for another installment.
The Christmas Chronicles 2: What Language The Elves Speak
Interestingly, you can see the construction for this language here.