From Tolkien Gateway

Their own word for themselves was Drughu, but the Elves adapted this into their own Sindarin language as Drû (from which the more common 'Drúedain' derives). From Sindarin, the word passed into Quenya, but again it was changed, and became . From this comes the plural form 'Rúatani' ('Rú-Men') which is the direct Quenya equivalent of 'Drúedain'.[1]