The official name of the emoji is simply “folded hand”. It was part of Unicode 6.0, released in 2010, codepoint U+1F64F. It’s on page 11 on the original proposal: www.unicode.org/L2/…/09026r-emoji-proposed.pdf

I guess they deliberately named it to the neutral “folded hand” so asian people can use as thank you, while westerners as pray