casement

Etymology

noun

1. A window sash that is hinged on the side.
2. A window having such sashes; a casement window.ᵂᵖ
   Passing through Tokenhouse Yard, in Lothbury, of a sudden a casement violently opened just over my head, and a woman gave three frightful screeches, and then cried, ‘Oh! death, death, death!’ in a most inimitable tone, and which struck me with horror and a chillness in my very blood. 1722, Daniel Defoe, A Journal of the Plague Year
   The street-lamps always burn; but scarce a casement / In house or palace front from roof to basement / Doth glow or gleam athwart the mirk air cast. 1873, James Thomson (B.V.), The City of Dreadful Night
3. (military) Occasionally seen as a usage error due to the similarity of the words: A casemate.