Dated term for a place to sleep, such as a bedroom or bedchamber. Modern Japanese more commonly uses 寝室.
In old houses, the sleeping place was a tatami room.
The birds returned to their roost in the evening.
Compound of 寝 (ne, 'sleep') and 所 (tokoro, 'place'), with rendaku voicing. The exact historical development is uncertain, but the word has been used since classical Japanese.