The Great American Novel
Russell and Silas were telling stories with Lego people.
R: Then my guy says, "Darth Vader, you shall FAIL!" and Darth Vader says, "No, I shan't!"
S, incredulously: Shan't?
R: "Shan't?" says my guy, "what the heck does shan't mean??"
—julie Thu May 31 22:46:23 2007
Shan’t = “Shall not”.
Kind of Shakespearian or “King James” speech, I guess. I'm not a native English speaking guy, but I think it’s the source of that kind of archaism. I'm not totally sure about this.