The Free On-line Dictionary of Computing (30 December 2018):

Java servlet
Java servelet
servelet
servlet

    (By analogy with "applet") A Java program
   that runs as part of a network service, typically an HTTP
   server and responds to requests from clients.

   The most common use for a servlet is to extend a web server
   by generating web content dynamically.  For example, a
   client may need information from a database; a servlet
   can be written that receives the request, gets and processes
   the data as needed by the client and then returns the result
   to the client.

   Applets are also written in Java but run inside the JVM
   of a HTML browser on the client.  Servlets and applets
   allow the server and client to be extended in a modular way by
   dynamically loading code which communicates with the main
   program via a standard programming interface.

   Servlets are more flexible than CGI scripts and, being
   written in Java, more portable.

   The spelling "servelet" is occasionally seen but JavaSoft
   spell it "servlet".  There is no such thing as a "serverlet".

   (http://java.sun.com/products/servlet/).

   (2002-10-06)