- A nonsense word of the Shire-hobbits.A non-existent month in the Shire calendar, used jocularly in the expression 'on Friday the first of Summerfilth', to refer to a something that would never happen. After the reform of the Shire's calendar in c.III 2670, each weekday always fell on the same date, and there was no month in the calendar that ever started on a Friday.The name 'Summerfilth' is taken from the real month of Winterfilth (approximately equivalent to our October).
J.R.R. Tolkien's Middle-earth glossary. MueRTe. 2003.