apple L was first uttered by Adam during one of the many AML MiniLANs. This event is captured in the video "minilan.wmv" around the 0:11 second mark.

Around the time he said it, Adam was trying to lock his computer (which anyone can do in Windows XP by pressing the Windows key + L at the same time). No one knows why he said apple L instead of Windows key L.

Around the 00:39 second mark, Adam realizes his mistake. "Apple L! Or... window L." Nevertheless, it's still a common slip made by the boys today when the subject of locking computers comes up.