Kendane͡ivash is the language of the Threadwielders. Part of the Threadwielder Commons, it acquires vocabulary whenever someone adds to said vocabulary.
A canonical dictionary can be found on the Tarnish website.
By inherent design, Kendane͡ivash is not a spoken language, but an encoded one. It's more comparable to UTF-8 Japanese characters than it is comparable to the rendering of Japanese glyphs. Indeed, glyphal alphabets for Kendane͡ivash vary from place to place, and pronunciation often starkly differs between cultures, where Kendane͡ivash is spoken at all. It's just as likely someone might encode Kendane͡ivash into light pulses or gestures.
If the mode of communication is not clear, the person initiating a conversation will begin with a recital of the Kendane͡ivash numerals until the other party acknowledges (or the initiator begins to suspect the mode of communication chosen is so unclear that the other party isn't even aware that communication is being attempted (or the communication attempt is outright invisible to their sensors)).
See also:
Threadwielders immersed in cultures tend to be multi-lingual, but since they cannot expect other Threadwielders to have the same background, their language tends to be maintained as a lingua franca between them, and they fall back to it whenever they visit one another for the first few times.
As such, the language is mostly used by Threadwielders themselves, though some words may sneak into sapient languages on worlds seeded by Threadwielders, because of their involvement.
The most notable users of the language are the kavkema, for whom - due to Evenatra's extreme presence during their cultural genesis - the language was something of a baseline and now continues to be used as a form of 'weakest encryption': While educated kavkema can speak the lingua franca of the Nayabaru (Naya), conversing in their “ancient tongue” (formally called Kendane͡ivash) can, in a pinch, buy them a few minutes head-start while someone struggles to translate on-the-fly.
That this “ancient tongue” is still actively expanded by them (causing there to be a slew of kavkem-specific Kendane͡ivash words) does not make them refer to it as anything else. The Nayabaru may sometimes call it kavkemic, though. Or, you know, “the language those terrorists use”.
See also: kavkem glyphs
WARNING: The following material has not yet had a chance to become canonical.
Some Draconic subcultures use Kendane͡ivash, especially when interacting with Threadwielders (i.e. almost surely Zalaagra), but knowledge of the language is much more spotty than it is with kavkema, as it is usually not the main tongue of the respective culture. In most places that are aware of Kendane͡ivash at all, the language shares a status broadly comparable to Esperanto with humans.