Sentries are posted at borders, gates, or doors.
The gentry (in this case to referring to the general populace) bar their doors at night.
The first month is January, named after the Roman god Janus, the double-faced God of doorways, passages and thresholds.
You pass through the doorway (hence the slip), and dun is a brown color, referencing the color of wood, which most doors are made of. Though it’s not commonly referred to, the “lip of the door” is the part of the door that fits into the doorframe on the handle/knob side, particularly if the door is lipped or ridged in order to fit the door frame better.

Thanks to Helena for creating this and sending it in.