TCM stands for the Toolkit for Conceptual Modeling. It is a suite of graphical specification editors that is intended to be used for software specification. But TCM is also very useful for drawing graph-like diagrams and for drawing tables.
The acronym TCM stands also for a number of other things
like Trellis Coded Modulation (encryption theory),
The Computer Museum (http://www.tcm.org
Traditional Chinese Medicine and the
Texas Chainsaw Massacre (a horror movie).
Obviously our TCM has nothing to do with all this.