Emilio Comici
It was the "Good Reverend" Henry Folsom who came up with the name back in 1971 so I thought it would be good to respect his innovativeness. He took about three months to do it with 19 effective hiking days. His goal was the shortest route on foot for all 48 without aid in between. The spelling has two "t's" and two "s's" in it......
And, before the "Good Reverend" Henry Folsom, there was Emilio Comici, who initially coined the term (sorry for my typo in spelling, as indeed Mats is correct about two t's and two s's).
Here is an excerpt from John Middendorf's excellent expose on big wall climbing, "The Mechanical Advantage." But, I had always heard Comici's quote as "......from the summit let fall a drop of my spit....." rather than "...drop of water....."
"In 1931, he put the new systems to use on the 4000 foot northwest face of the Civetta. This was the steepest and perhaps the most difficult climb in the world at the time (and is still to this day is a challenging 26 pitch vertical adventure), but not satisfied, he wrote "I wish some day to make a route and from the summit let fall a drop of water and this is where my route will have gone." He realized his dream of such a route, a direttissima as it became known, with his direct line up the 1500 foot overhanging north wall of the Cima Grande in 1933. The line wavers slightly but no more than if the mythical drop of water were buffeted back and forth by an unseen wind. On the steep initial half of the wall, Comici and Giulio Benedetti used just 75 pitons -- on average only one every ten feet -- hardly excessive considering that the wall overhangs continuously and is composed of less-than-solid rock."
http://www.bigwalls.net/climb/mechadv/index.html
Probably the most famous "direttissima" is the Eiger's North Face ("Of course" - Clint Eastwood
). But, these guys have the authorship all screwed up on the namesake book by Dougal Haston and Peter Gillman.
http://www.librarything.com/work/1164617