Maltz was the sole survivor of the Klingon Bird of Prey that attacked the Enterprise in orbit around the Genesis Planet. He was captured by Admiral Kirk and his officers and brought back to the Federation as a prisoner.
Since that incident, Maltz has cooperated in aiding the Federation to better understand the Klingons and their language. It is through his efforts that most of our knowledge of tlhIngan Hol is derived. When Marc Okrand gives us new information about Klingon, he has gleaned it from conversations with Maltz.
Maltz' name is pronounced matlh in Klingon.