Munnion

Part of speech: noun

Definitions

1. A slender vertical bar of stone or wood that divides a window into separate panes or lights, common in Gothic architecture
2. The upright member that splits a window opening into smaller sections, often found in medieval church and castle architecture
3. An architectural post running vertically between window lights to support the tracery and divide the opening into parts

Etymology: "Munnion" is an archaic spelling of "mullion", the upright post that divides a window into separate panes. The form has come down through a tangle of changes. The word traces back to Old French "moinel", a diminutive of "moine" meaning "monk", so the vertical bar that splits a window shares its root with a word for a religious man. Middle English had its own versions, "moyniel" among them, and English speakers reshaped the word in two ways. One route altered the sounds of the Old French form into "monial", and the other swapped the position of sounds within "moyniel", a process linguists call metathesis. Both paths led toward the "mullion" we use now, and "munnion" survives as an older spelling of the same post.