I think the makers of the film called the ‘Saw’ films by that name just so people could have the following conversation:

A: Did you see Saw?
B: Yeah, I saw Saw.
A: Did you see Saw 2?
B: I saw Saw 2 too.
A: Did you see Saw 3?
B: No, but I saw Saw 4.
A: What did you see Saw 4 before you saw Saw 3 for?