How did they come up with the title?

Well, I mean, it's the character's name, obviously. But how did they decide to name the character that? I think they wanted to use a tagline, something like this:

Is he a clod?
Does he have a clue?
No! It's Klute!

(Really enjoyed rewatching this, by the way. For those who say they don't think it's a thriller, give me a break. What movie is more thriller than this? It's a definite thriller.)