Ayyup, went and found this

Inoue: “The world of Splatoon takes place 12,000 years after the present time and the Squid Sisters are those who receive messages from 12,000 years ago. Like there would be a discussion ‘rice or bread?’ in current time, and those words fly to another planet and bounce back for them to receive. Those divine messages come from kami-sama”

Nogami: “Kami-sama is written as ‘paper’ when using kanji [kami has several meanings, two of which are a god and paper], so the topic of Splatfest comes as a fax-like paper. That’s where the name kami-sama comes from (laughs).”

Also, the bit about squid sisters' before the game became final

Originally, before they were idols, they were called ‘shrine maidens’ and their role was to transmit divine messages from god to people.”