feature-file

feature-file is a compiled Lisp function in `loadhist.el'.

(feature-file FEATURE)

Return the file name from which a given FEATURE was loaded.
Actually, return the load argument, if any; this is sometimes the name of a
Lisp file without an extension. If the feature came from an `eval-buffer' on
a buffer with no associated file, or an `eval-region', return nil.