What does the root word stetho mean?

The root word "stetho" comes from the Greek word "stethos", which means chest.

This is why you see it in words like:

* Stethoscope: An instrument used to listen to sounds within the chest, particularly the heart and lungs.

* Stethometry: The measurement of the chest.

So, essentially, "stetho" refers to anything related to the chest.