Server-side JavaScript (SSJS) refers to JavaScript that runs on server-side. This term was coined because the language was originally limited to just client-side, i.e. client-side JavaScript (CSJS).
The first implementation of SSJS was Netscape's LiveWire, included in their Enterprise Server 2.0 product, released in 1996.
Examples of current uses of JavaScript on the server include Helma Object Publisher, using JScript as an ASP scripting language and the Ruby-on-Rails-like TrimJunction.