Harold was named by the Cast Members that work the Matterhorn. It should be the Expedition Everest Cast Members that name him, and then they can come online and tell us what his name is.
But I don't think it should be Harry or Herman; no "H" names. It would sound too much like Harold, and Harold is so famous in SoCal that it would just sound like the WDW'ers were trying to copy Disneyland.
The Cast Members deserve to name their Yeti. They should probably stay away from the names that start with "H" to avoid upsetting Harold.