Definition of plaque

The etymology of the word "plaque" has its origins in Old French, where it was spelled as "plaque" or "plaquette." In medieval French, a "plaque" referred to a small flat piece that could be mounted on a larger structure or used as a decorative element. The word's meaning evolved over time, and by the 16th century, "plaque" began to signify a specific type of flat, decorative item used in armor. It was often made of metal, such as steel or silver, and affixed to a shield or breastplate as a form of aesthetic accent. In the 18th century, "plaque" took on another meaning: that of an engraved or carved relieve plaque. This usage of the word can be seen in architectural contexts, such as ornamental wall plaques or commemorative signage that is staffed or mounted. In the late 19th century, the term "plaque" was applied to biofilms, the slimy aggregations of microbes that grow on the surface of objects. This modern-day usage of "plaque" to describe a buildup of bacteria appears to have originated from its earlier meaning as a decorative, embellishing element, as biofilms often take on a coating-like appearance. Overall, "plaque" has had a diverse history, evolving from a small decorative item in medieval armor to a range of meanings in modern contexts from decorative elements to medical and scientific terminology.