Tester: a word I first came across last week.

Before the advent of window-glass, 
birds and bats (maybe flying foxes)
could fly into the bedrooms of the rich.

A tester (presumably connected
with French teste or tête),
was the covering of wood or material
(not quite a baldaquin)
supported by the posts
of a four-poster bed
(lit à colonnes in French) to prevent
the occupants being shat upon.

Curtains kept out the considerable
draughts from glassless windows.

Such beds are mentioned in Old Irish sagas.