I've just been reading "The Mythical Man Month" by Fred Brooks. Some people think his book is brilliant other people deride it with comments such as "it taught me nothing new".
Those who deride it should look at the publish date. It was written in 1975 based on 25 years in the computer industry. I have the copy with the 1995 adendum. My point being that the book is the IT equivalent of Genesis.
You can clearly see the germination of ideas that are now part of agile development. For example Harlan Mills advocated an itterative approach back in the 1970's and he wasn't the first. From what I can gather the idea of iterative development dates back to the 1950s.