Think further back then the rosary peoples. My understanding is that this originally started in the orthodox church.
In the orthodox church, the sign of the cross is very specific. The thumb and forfefinger are to cross, creating a cross. The remaining three fingers stick out to represent the trinity. Then on the “Holy Spirit” part, they go from right shoulder to left(instead of left to right) to end over their heart. At the end of the sign, they kiss the cross made with their fingers.
Catholics then picked up on this using their rosaries and/or holy water.
Josh