The name is from a character in the Jack Ryan series by Tom Clancy (yes, they are books). "Clark" is a character that first shows up in The Cardinal of Kremlin. His roles after this story were much bigger. John Terrance Clark is a special ops guy who works for the CIA. He's a real bad ass character. There are two books that work in tangent to the Jack Ryan series, I wouldn't call them spinoffs. Without Remorse tells about his background, this is the one where people really love the guy. The other is Rainbow Six. If you don't know here's the entire series:
The Hunt For Red October
Patriot Games
The Cardinal of Kremlin
Clear and Present Danger
The Sum of All Fears
Without Remorse (takes place before all others, but written here)
Debt of Honor
Executive Orders
Rainbow Six
The Bear and the Dragon

Four of these have been made into movies, I hope they do one of Without Remorse. I haven't seen The Sum of All Fears Yet, but of the other three (if you don't know which ones they are drop dead) Clark is only in Clear and Present Danger. He's played by Willem Dafoe.