The extension language of JamesGosling's implementation (Unipress) of the EmacsEditor. The name is presumably a pun on MacLisp, the extension (and implementation) language of MulticsEmacs.
http://www.jwz.org/doc/emacs-timeline.html gives a family tree of Emacsen.
Oh, I was expecting the imperative form, here!
Contributors: DonaldFisk