Deep is the layer being worked, not how hard the practitioner pushes.
In 📝Deep Tissue Massage the word locates a plane under the surface — a muscle belly, a septum, a place that will not glide — not a license to lean harder. Force without a warm surface makes the body guard; a slow, heavy contact that the tissue accepts can reach a deeper layer with less effort. Deep is a description of where the hands are, not a diagnosis and not a contest of pressure.
Clients often hear "deep" as "painful." Session language has to separate layer from force. If the person cannot breathe, the contact is too much, whatever layer was intended.