As Mortar said, it's short for "Dulux-Oz Extension" (and for the record: DOM = Dulux-Oz Module). I label all my Extensions (& Modules) with the "DOE" suffix ("DOM" suffix) both as a piece of "branding" and also to indicate that I wrote them, so people know that if they like one of the DOEs they'll probably like the others, and also that all the DOEs have been written and tested to work with each other - something not guaranteed with Extensions by different authors/developers.
Its also easier to write (& to say) "DOE" than it is "Dulux-Oz Extension" :)
Does that clear things up?