principal : Java Glossary
Some way of measuring the identity of some code. For example, Codebase principals refers to code identified by its codebase (file or
HTTP (Hypertext Transfer Protocol) url). Certificate (or signature) principals refers to code identified
it’s having a digital signature. Once you have identified the code, you can
describe a policy of what actions it is permitted to do. When you compare this jargon
in Java to the jargon used in the emerging MS .net
framework, principal is referred to as evidence in
.net which seems like a more intuitive word to describe the idea.