I was going to try to post links to all the threads we’ve had about this in the past, but it’s a bit daunting. This is, shall we say, one of the Great Questions of the SDMB.
Instead, I’ll just give you the most recent 5 threads. The fifth one has an excellent set of links in the second post to many more discussions here.
As of now, I believe the earliest reference in print of this phrase is the one discovered by our own samclem, which is referenced in the OP of the third link above. It is from 1964, which makes the kilt theory implausible.
Sam’s discovery includes not just the phrase in print, but a definition. It is stated to be space-program slang for a line-by-line report on a project.