A lozenge is a parallelogram which usually has two corners pointing up and down that are farther apart than the corners pointing sideways. It is often used in parquetry and as decoration on ceramics, silverware, and textiles.
During the First World War, the Germans were looking for a way to effectively camouflage their aircraft. This resulted in the development of the so-called lozenge pattern, made up of irregular painted polygons. Because painting such a pattern was very time consuming, and the paint added considerably to the weight of the aircraft, it was decided to print the pattern on a fabric. This pre-printed fabric was used from 1916 onwards, in various forms and colours, like the one pictured below.
A lozenge is also a tablet which you can suck when you have a cough or sore throat. Lozenges contain medicine that helps to reduce the pain or irritation. The name for such a tablet (first used in 1530, according to the SOED) derives from its being originally lozenge-shaped. Today one of the most popular brand names is Fisherman's Friend, produced in Lancashire, England since the 19th century.