This is very noticeable in the Athrabeth, where Finrod switches between "you" and "thou" when talking to Andreth throughout the conversation. Tolkien also talk

This is very noticeable in the Athrabeth, where Finrod switches between "you" and "thou" when talking to Andreth throughout the conversation. Tolkien also talks in Appendix F of The Return of the King about how hobbits had largely lost the distinction between "you" and "thou" - so when Pippin speaks to Denethor in Minas Tirith and addresses him with the familial term, people assume that he must be royalty himself to address the Steward in such an informal manner.