You could run a trace or profiler (with filters if required to eliminate noise) and look at the various columns in the profiler output - such as Application Name, NTUserName, Login Name etc. to get an idea of what/where the calls are coming from. What you see may depend on how the caller is connecting. For example, the Application Name is something a caller can set in the connection string if they choose to. If they have not set it, it might return you something generic.
If you need to capture/store that information in a production environment regularly, the stored proc would have to pass in the caller name as a parameter.