What does the Eternum skin line mean?

Rek sai and Nocturne have eternum skins. I just read a Riot feature about the PROJECT skins, it compared them to Mecha and Battlecast, how they are futuristic and "tech"

I have no artistic soul, so other people have to tell me. What is the eternum skin line about? It seemed like robot-ish kinda stuff to me too. Or is it just these insects have their carapace removed and steel armour replacing it?