recentf-arrange-by-rule-others

recentf-arrange-by-rule-others is a variable defined in `recentf.el'.
Its value is

"Other files (%d)"

Documentation:
Title of the `recentf-arrange-by-rule' sub-menu.
This is for the menu where items that don't match any
`recentf-arrange-rules' are displayed. If nil these items are
displayed in the main recent files menu. A '%d' `format' pattern in
the title is replaced by the number of items in the sub-menu.

You can customize this variable.