I note that one's own anatomy and its functions have both Latin and Anglo-Saxon names, the former being "proper," the latter "vulgar." Yet, it seems to me, we tend to use the AS words for bodily functions when said function's particularly satisfying, or when it's intended pejoritively, and the Latin correlate when speaking neutrally. The American writer Diane Ackerman makes this point quite well in her book, "A Natural History of Love."