IN SIDE OUS = INSIDIOUS
Thats my guess. Josh has something Insidious is trying to get "inside" him in Chapter 2
and something insidious is trying to get "inside" of Dalton.
Inside us, Demon is a puppeteer and we are the puppets. Marionettes and puppets in his room suggest this also. He
wants to be inside us.
It was their slogan if you will for the trailer. Insidious IS Insidious. The words would flip forwards and backwards and the IS would remain. I have no idea why they chose that as their slogan though.
I think si is an abreivation as u kno he falls asleep. So the answer is SHUT IN. See
SI... see it? First thing I thought of but I don't know.. it could mean a lot of things with something so vague..
Never heard of the movie or saw the poster until now when I looked it up, the way it was written sideways like that and the red SI for some reason made me read it as "inside" the first time, though letters like to dance around on me alot so that might of been nothing intentional.