In order to reach Nobodo, the Grappling Hook is required. In the Anouki Village (i.e. not in the Great Ice Field or Temple of Ice approach), go to the south-western part, near the boat. There are some pegs, onto which Link can jump and grapple to reach an elevated platform with a single Anouki standing on it.
If Link talks to Nobodo, he will comment on being sad. He will also be offended that other Anouki call him "No-Abodo", because he has no abode. He will then say that he actually likes being sad. The real reason why he is useful, though, is because he tells Link that other Anouki - those WITH houses (he refers to those in the Anouki Estates, not to the ones located around the island) - often burrow treasures in front of the signs near they houses. As implied, digging in front of the signs in the Anouki Estates will unearth some valuable Rupees. Note that it is not necessary to speak with him if Link already knows this information.