Obviously its not a weird hand position but the fact it is used in christian prayer (atleast for a few hundred years) and in japan for praying at Shinto shrines (or just in general) and im sure other places seemed interesting to me. Did they influence each other or did this hand position come about independently?
In most of Asia, including Japan, the gesture stems from the Indian Anjali Mudra gesture. It spread into the rest of Asia with Buddhism.
It's origin in Christianity is unclear, but seems to stem from Jewish roots.