"In Japan the fear of being led astray by an untrustworthy spirit-fox is so pervasive that a set of social conventions has arisen by which people can assure one another of their humanness. In telephone conversations such assurances are especially important, since the two parties cannot see each other and have to rely entirely on verbal codes. One convention has it that foxes cannot pronounce certain sounds in human speech, such as the phrase ‘moshi moshi,’ which has come to be the standard telephone greeting and has no real meaning beyond demonstrating that the speaker can make non-vulpine sounds. In effect, then, the greeting means ‘rest assured that you are not speaking to a spirit-fox who might trick you.’"

I typed all this out by hand I was so delighted to find it in this excellent book about foxes.