Kobolds were natives of the planet Procyon Two. When the TARDIS materialised on Procyon Two, it started to alter the Kobold language, but the job was only partially finished when the Time Lords brought the Third Doctor back to his exile on Earth. As a result, the Kobolds could only use the vowels "o" and "y".
Three Kobolds, Two, Forty and Forty-Two came to Earth to take over the TARDIS, but only Forty-Two survived. (PROSE: Morphology)