noun
garret
GAR-uht/ˈɡærət/
A small attic room, especially under a sloping roof.
The garret fits a small bed beneath its low sloping ceiling.

Etymology
Garite meant a watchtower or shelter, and English garret first named a small tower on a roof. The name then shifted to a room on the uppermost floor, especially beneath a sloping roof.
In context
on the staircase. His garret was under the roof of a high, five- storied house and was more like a cupboard than a room.