Neko Atsume word of the day サコイチ

Hello,

I still play Neko Atsume, in which you can submit a secret word of the day for some extra coins.
Today's word was サコイチ, and I usually like to look up any words I don't know to learn a new vocab of the day.
Unfortunately, I haven't had much luck today as I've mostly just found someone's online username and nothing else coherent, and it does not seem to sound like anything phonetically. Does anyone know what this could be?

by Pep95