Oh my gosh, I love headcanons surrounding Murdoc's vocal tics. I tend to imagine that they are due to intrusive thinking and identity threat, which I began ticking from. Like, every time a thought pops up that he feels implicates him badly, he makes a noise or distorts his speech, as a way of showing guilt or detachment from the thought. It's confusing to everyone else, because they obviously can't see his thoughts. I also headcanon that Murdoc is half Georgian, in terms of race.