Winterfilth was the tenth month of the Shire Calendar, approximately equivalent to modern October (in fact running from 22 September to 21 October on a modern calendar).
This month was called Wintring in Bree. It was a jest in Bree to speak of "Winterfilth in the (muddy) Shire"
The name referred to the completion of the year ("filling") before Winter in their old calendar (before they adopted the King's Reckoning) when their new year began after harvest.
The name actually represents a modernization of the Old English name for October, Winterfylleþ, meaning "Winter-filling" or "Winter-full moon".
 See also
- ↑ 1.0 1.1 J.R.R. Tolkien, The Lord of the Rings, Appendix D, "The Calendars"
- ↑ Arden R. Smith, "The Shire month-names", Mellonath Daeron - The Language Guild of the Forodrim (accessed 26 September 2017)