Hour Five: the forty days
Nudge. You named this day once already, on the first night, to a gentleman at the shutter.
Harder
Forty days from the second of October: twenty-nine in October and eleven in November. The eleventh of November is the feast of St Martin.
The answer
The word is martinmas.
The house was shut up on the second of October 1665 till forty days be past, which ended on the eleventh of November: Martinmas, as the almanac in Part 1 named it.