American linguist (born 1948) who devised the spoken Klingon language for Star Trek III: The Search for Spock and wrote The Klingon Dictionary, turning it into a usable constructed language.
Marc Okrand (born 1948) is an American linguist who specialised in Native American languages. His first Star Trek job was writing Vulcan dialogue to be dubbed over a scene in Star Trek II: The Wrath of Khan.
For Star Trek III: The Search for Spock he was asked to build a full Klingon language, starting from the few harsh-sounding lines James Doohan had invented for Star Trek: The Motion Picture. He gave it an unusual sound system and an object-verb-subject word order, and published the grammar and vocabulary in The Klingon Dictionary in 1985.
Okrand returned as language consultant on later films, including Star Trek V, Star Trek VI and the 2009 Star Trek, and his Klingon remains the basis of the dialogue heard in the modern series.