how to reference the current *.el file in elisp

[Harry Putnam]

How does elisp reference the current *.el file?... I mean like in the
way that the variable $0 carries the the value that is the full name
of the script its in.
What I'm really after is a say to to add that value to a message
('(message "hello")')

Like this message (wrapped for mail):

(message "hello world -- from
 /cvsb/reader/home/reader/lisp/site-start.el")
 (sit-for 1)

that I use sometimes when tracking down how things are loading.

How can I reference the name in a variable instead of writing it out?