Originally added to the upstream compose map in https://gitlab.freedesktop.org/xorg/lib/libx11/-/commit/f052..., and replaced in https://gitlab.freedesktop.org/xorg/lib/libx11/-/merge_reque.... Given the people involved in the initial commit, I suspect (but do not have an absolute memory of) it may have been influenced by my ownership of (insert a hammer and sickle symbol here).net.