The Taelon language was a language used by the Taelons.
Originally considered to complex for humans to learn to speak, James Pike was able to reconfigure his CVI to assist in learning ancient Taelon. Pike demonstrated his ability to speak Taelon in a communication with Companion Da'an. Pike, who was given the CVI as part of a prison rehabilation program, was at the time being pursued by William Boone after he escaped said prison.
It was known that their species lacked even a word for the Atavus creatures from which they originally evolved from and had been expunged from their language. The closest term that they used for their early ancestors was the Earth latin word "Atavus" though even it failed to convey the horrors that such beings were capable of accomplishing. (Episode: Atavus)