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.