From C-h v This variable was introduced, or its default value was changed, in ve...

b3n on April 15, 2020 | parent | context | favorite | on: Emacs: The most successful malleable system

From C-h v

    This variable was introduced, or its default value was changed, in version 22.1 of Emacs.
    Probably introduced at or before Emacs version 20.1.