【Catalina】

Tomcat's servlet container was redesigned as Catalina in Tomcat version 4.x. 

The architect for Catalina was Craig McClanahan. 

这是wikipedia的解释,即Tomcat的servlet容器在4.X版本中被Craig McClanahan重新设计为Catalina.说白了,Catalina就是servlet容器.

显然CATALINA_HOME就是Tomcat运行时的环境变量,和ANT_HOME以及JAVA_HOME相类.