footnote-section-tag-regexp

footnote-section-tag-regexp is a variable defined in `footnote.el'.
Its value is

"Footnotes\\(\\[.\\]\\)?: "

Documentation:
Regexp which indicates the start of a footnote section.
This variable is disregarded when `footnote-section-tag' is the
empty string. Customizing this variable has no effect on buffers
already displaying footnotes.

You can customize this variable.