For anyone who wants to know more about the GEKs or how their names are derived, the first place of stop is Regardie's "Golden Dawn" book. However, it's somewhat confusing on the matter, so I'll share an Inner Order O.'.S.'.D.'.L.'. document. Technically the likes of this would be reserved for Adepts, so I caution you to use with care (if at all), but I think it's better to share what I can so that genuine students have access.
The document is attached. You'll note the old Seal of the Order, so you can tell it's an old document. The information is still perfectly valid, however.
LLLSHJ,
Yechidah.