GUI Cookbook

Vertical-vertical-hierarchical menus appeared for the first time on 12 Oct 1988, with the release of NeXTSTEP 0.8 (the operating system for Steve Jobs' NeXT computer) and introduced the idea of a vertical menu strip in the upper left-hand corner, which could also be "torn off" at any point so that the user could create specific menus and place them anywhere in the screen (A behavior still practiced on the toolbar’s of Adobe products). The menu was that way disassociated from the application window, with the benefit of not overlapping the content being edited.

Horizontal-vertical menus will not undergo any other dramatic evolution until October 12th, 1988, with the release of NeXTSTEP 0.8 (the operating system for Steve Jobs’ NeXT computer) which introduced the vertical-vertical-hierarchical menu as well as the concept of one-click to drop and maintain the menu in place (until a choice in the menu items was done, a common and default practice today) which was a departure from the previous theory of click-and-hold of the mouse button used in the Lisa, Mac and other operating systems at the time.

Resources:
http://www.guidebookgallery.org
http://www.blooberry.com/indexdot
http://toastytech.com/guis/index.html
http://www.operating-system.org
http://www120.pair.com/mccarthy/nextstep/intro.htmld/