Why did Miss Sullivan repeatedly spell w-a-t-e-r into Helen's hands while pouring water over them?

Miss Sullivan spelled "w-a-t-e-r" into Helen's hands to help her make the connection between the letters she felt and the Word being spelled out. By combining the tactile experience of feeling the water and the visual input of seeing the letters spelled out, Helen could start to understand the concept of language and communication. This method was a breakthrough in teaching Helen how to communicate effectively.