the.com/dormer window

means A window set vertically in a structure that projects out from a sloping roof, letting light and headroom into attic spaces.

from From 'dormer,' rooted in Old French 'dormeor' meaning 'sleeping room,' which traces back to Latin 'dormire,' 'to sleep' — the same root that gives us 'dormant' and 'dormitory.' The name makes sense once you picture the room behind the window: attics were historically where people slept, tucked under the roofline, and the window that poked out to give that sleeping space light and air simply inherited the room's name.