[Kevin_Marks]

The use as a menu button dates back at least to the Sidekick II: http://en.wikipedia.org/wiki/File:SidekickII.jpg (though that has one long and 2 short lines).

[dfox]

It was used long time before that. Many TUI DOS aplications (especially Turbo Vision based or copying Turbo Vision UI style) use this character for leftmost item of menubar with "system" things and utilities like calculator (obviously inspired by Mac OS's Apple menu).