It's an invention. It was first developed in the early 1980s, and quickly replaced "creationism" in YEC efforts to get their doctrines imposed on public schools:
The most common modern use of the words "intelligent design" as a term intended to describe a field of inquiry began after the United States Supreme Court ruled in 1987 in the case of
Edwards v. Aguillard that it is
unconstitutional for a state to require the teaching of creationism in public school science curricula.
[11]
A Discovery Institute report says that Charles B. Thaxton, editor of
Pandas, had picked the phrase up from a
NASA scientist, and thought, "That's just what I need, it's a good engineering term."
[34] In drafts of the book, over one hundred uses of the root word "creation", such as "creationism" and "Creation Science", were changed, almost without exception, to "intelligent design",
[12] while "creationists" was changed to "design proponents" or, in one instance, "
cdesign proponentsists" [
sic].
[11] In June 1988, Thaxton held a conference titled "Sources of Information Content in DNA" in
Tacoma,
Washington,
[27] and in December decided to use the label "intelligent design" for his new creationist movement.
[24] Stephen C. Meyer was at the conference, and later recalled that "The term
intelligent design came up..."
[35]
Intelligent design - Wikipedia