Because the actor actually said "animal" Okrand had to make up a Klingon word that would lip sync, that's how animal turned into Ha'DIbaH
Specifically, this was in
Star Trek III - The Search for Spock, which was the first movie that Okrand made Klingon dialogue for. He had previously been hired to do the same sort of thing for the Vulcan dialogue in
Star Trek II - The Wrath of Khan; they'd already recorded lots of scenes in English, and didn't want to reshoot them, so he wrote alien dialogue that matched the already recorded lip movements so that they could solve the problem with voice-over recordings.
Source: http://www.youtube.com/watch?v=-yUWnhw0WeA#t=2m3s