I tried googling this but nothing came up until I stumbled across https://en.wikipedia.org/wiki/DOS_MZ_executable https://en.wikipedia.org/wiki/DOS_MZ_executabl

I tried googling this but nothing came up until I stumbled across https://en.wikipedia.org/wiki/DOS_MZ_executable https://en.wikipedia.org/wiki/DOS_MZ_executable which says it stands for Mark Zbikowski (which is supported by a quick Google of that name).