Looking upwards to express disbelief

Why is looking upwards used to signal disbelief (as in this: :rolleyes: )?

Why upwards, and not, say, downwards? What is the origin of this?

Just a SWAG, but I thought it was looking up to Heaven for strength and patience…

Same here. I’ve always thought of it as the non-verbal equivalent of “Dear Lord, why must I listen to such drivel?”