8 Words That Are Older Than You Think
A component of an HTML page, that contains directives, layout, and code in a single context. A pagelet may be a separate file or web page that contains information you want displayed across several pages. They are similar to server-side include files, as implemented in ASP+. Pagelets act like independent HTML frames and provide discrete access to content. They use Cascading Style Sheets as templates for defining their layout behavior in a single context.
[.NET Framework Essentials, 2nd Edition, Thuan L. Thai and Lam Hoang, February 2002, 0-596-00302-1]