Literally never heard that prior to hacking on the mg codebase.

In GNU Emacs, try running M-: (dot) RET.

I think this alias was an aid to porting Lisp from some other Emacs variant in the 80s that used "dot" instead of "point". Never figured out which. It isn't mg because mg doesn't run Lisp.

also in sam and acme editors in plan9 os

Emacs called it “point” which is not as far. The cursor is just the visible widget.