“Above the fold” origin

Information Design, Patterns

The term was first used in reference to traditional media, newspapers to be precise. The thinking is that newspapers are often delivered or displayed folded up and the area ‘above the fold’ will be the first that the reader sees and it is therefore a prominent and important location.

http://webdesign.tutsplus.com/articles/design-theory/designing-for-the-new-fold-web-design-post-monitorism/