The language spoken by the Sljee people was known as Sljee, originating from their homeworld of Sljee.
Sources
An article on Wizards.com titled "Jeseej and the Sljee: Coruscant and the Core Worlds Preview #7" discussed this (though the content is outdated; backup link provided).
The book Coruscant and the Core Worlds also contains information.
Appearances
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