Why is Kaddish not in Hebrew?

[americani]

When listening to someone say it it seemed off and someone explained it isn't in hebrew but aramaic(spelling?, not arabic) is this a preference of the group that created the Siddur we were using or for some other reason?

[rosends]

here is some reading on the matter

https://www.chabad.org/library/article_c...t%20prayer.