Ekaagan,
By "code words" I assume you mean "ELU" and "SKU". These mean, respectively, "end line user" and "stock keeping unit".
Any person or entity that buys knives is a customer, so Spyderco uses the term "End line user" do distinguish regular customers like you and me from other buyers--wholesalers and retailers--who buy knives but don't actually put them in their own pockets.
A "stock keeping unit" is a particular version of a knife. Take the Endura, for example. You can get it in the following :
1. Zytel handle, plain edge
2. Zytel handle, serrated edge
3. Zytel handle, plain/serrated edge
4. Steel handle, plain edge
5. Steel handle, serrated edge
6. Steel handle, plain/serrated edge
That's six "SKU's". From the manufacturer's standpoint, it's difficult and expensive to produce and maintain inventories of so many different varieties of everything. The ELU's want endless variety, and Spyderco wants to make us happy but not tie up machines and warehouse space with knives only a few people will buy.
I hope this helps.
David Rock