There are a lot of data on the intercorrelations of fears. I once spent months trying to get the fear of public speaking into the schema of fear of death versus fear of anxiety, but I couldn't do it and had to conclude fear of rejection/ embarrassment is a third kind of fear.

The fear of public speaking is less correlated to the fear of death than are many other fears. The fear of public speaking is about self-concept; fear of rejection. Most fears are not about self-concept.

Basically, fears cluster into three groups: the fear of death/injury, the fear of anxiety/pain, and the fear of humiliation/embarrassment. Fear of public speaking is most strongly related to fear of humiliation/ embarrassment.