/fɪˈnɛstrə/
[noun] A small window-like opening in a bone or other body part, especially one of the two membrane-covered openings in the inner ear. The word is also used in architecture and biology to describe any small hole or gap that looks like a window.
Every time you hear a sound, it travels through tiny holes in your skull that the Romans named after windows.
The story of 'fenestra' begins in classical Latin, where the word simply meant 'window' — that opening in a wall through which light and air could pass. Roman writers used it freely and practically, and the word appeared throughout Latin literature to describe the windows of homes, temples, and public buildings. Its ultimate origin is uncertain, but many scholars believe it may have been borrowed from an Etruscan source, making it one of those fascinating words that arrived in Latin from the mysterious, poorly understood language of the Etruscans, Italy's pre-Roman civilisation. A connection to the Greek 'phainein', meaning 'to show' or 'to bring to light', has also been proposed, though this remains debated.
As Latin spread across Europe and eventually fragmented into the Romance languages, 'fenestra' transformed along different paths in each daughter language. In Old French it became 'fenestre', and from there it entered Middle English briefly as 'fenestre' before being largely displaced by the Germanic word 'window', which had arrived with the Norse-influenced Anglo-Saxon vocabulary. The French path also gave us 'defenestration' — the dramatic act of throwing someone out of a window — through the chain Latin fenestra → Medieval Latin defenestrare → modern English defenestration, a word that became famous after the 1618 Defenestration of Prague, when Protestant noblemen threw Catholic officials from a castle window, sparking the Thirty Years' War.
In the architectural tradition, the Latin root was never entirely forgotten by scholars and builders. The adjective 'fenestrated', meaning 'having windows or window-like openings', remained in learned English use, and the related word 'fenestration' came to describe the arrangement and design of windows in a building — a term that architects still use today. These words came directly back into English from Latin fenestra, carried by the Renaissance habit of reaching back to classical sources for precise technical vocabulary.
The word took on a remarkable second life in anatomy and medicine. When early anatomists examined the inner ear, they discovered two small membrane-covered openings in the bony wall of the cochlea, and they named them after windows, borrowing directly from Latin. The 'fenestra ovalis', or oval window, and the 'fenestra rotunda', or round window, transmit sound vibrations from the middle ear into the fluid-filled chambers of the inner ear. Without these tiny 'windows', human hearing would be impossible. The word was brought into English medical usage in the 17th and 18th centuries as anatomists writing in Latin gave formal names to the structures they described, and those Latin names stuck.
Biology and zoology also embraced 'fenestra' as a technical term to describe any thin, translucent, or perforated area that resembles a small window — in insect wings, in plant leaves, and crucially in the skull bones of animals. Palaeontologists use 'fenestrae' (the Latin plural) to describe the openings in the skulls of dinosaurs and other prehistoric creatures. The number and position of these openings is one of the key features scientists use to classify ancient animals, making fenestrae essential to our understanding of evolutionary history. So a word that once simply described a hole in a Roman wall now helps scientists decode the family tree of life on Earth.