Because they couldn't be categorised as skinny. They are more slim but it's just diesels way of best describing their product in their own way. And zahi, just search for diesel master cut list here and it gives a list of every cut past and present in terms of loose to slim.
-ne means joggs and -a is fashion pants. I've given up on trying to figure out diesels coding system and when I enquired on behalf of here they told there is no system. And the acronyms mean nothing either do the alpha numeric wash codes. It's just a thing for differentiating during manufacturing.