Hi Hal, I thing there are families that use Rainwater and also that use Rainwaters. I've also found that even within the same sibling group that they use both. One brother will use Rainwater and the other, Rainwaters.They are used interchangeably. A lot of times it was written down by a clerk in a record office and that's the way the family used it, especially if that person could only make "his mark". Glidie