INCLUDINGTOPIC -- name of topic that includes current topic

The name of the topic that includes the current topic - same as %TOPIC% in case there is no include. If a topic is used in a chain of INCLUDEs, INCLUDINGTOPIC is set to the topic directly INCLUDing this one, NOT the topic that has been requested by the user (which is given by BASETOPIC)

Be careful of the subtle difference between INCLUDINGTOPIC and BASETOPIC. You probably should be using BASETOPIC

Related

BASETOPIC, INCLUDINGWEB, INCLUDE, TOPIC