Boeing DDG History

[framer]

While reading the DDG for the 737NG I came across this statement at the start of the manual:

The Boeing DDG has been developed as operators have found difficulty in developing procedures required by the MMEL and identifying missing parts from the CDL. They have often consulted Boeing for guidance in these areas and as a result, this document was prepared for reference.

I am interested to know when the DDG was first developed? I wonder if 737 pilots in the 90’s were struggling away with an MEL document that was difficult to interpret or was it the 70’s or 80’s ? If anyone knows the history it would be great to hear.
​​​​​​​Happy 2026 everyone