An archaic day-name from the Common Tongue as used in the Shire. It referred to the second day of the week, which was named in honour of the Sun. Over the centuries, this name evolved into the more familiar form 'Sunday', which was the usual name at the end of the Third Age. Its roots lay in Elvish, where the second day of the week was also dedicated to the Sun: in Quenya it was named Anarya, and in Sindarin it was Oranor.
Notes
1
This date is based on a comment in Appendix D to The Lord of the Rings, where we're told that they were in use 'at least nine hundred years before Frodo's time'.