The 1891 patent for the toilet paper roll literally states that the end of the roll should be hanging off the exterior, in other words, it should be placed in the ‘over’ position.
Additionally, how do beginners use toilet paper?
Take the paper around and behind your bum and lean to the facing cheek. Clean up with index, second, and ring fingers. Raise your middle finger by half-inch while your index and ring finger slightly resting behind you. Wipe slowly from front to back and ensure you apply a reasonable amount of pressure.
Consequently, why toilet paper goes over and not under? Over is generally the intended direction of viewing for the manufacturer’s branding, so patterned toilet paper looks better this way. Under provides a tidier appearance, in that the loose end can be more hidden from view.