These days this item of clothing is usually made from denim and has a bib-like flap that covers the chest, held in place by shoulder straps. Dungaree, in the singular, is first recorded as a type of calico cloth during the 17th century. The OED gives the source word as the Hindi dungri, a type of coarse cloth. Eric Partridge in his Dictionary of Slang maintains that Dungri was the name of the suburb of Bombay where the cloth was first made. In any event, like so many other words in English, the origin is Indian and was first used only in the singular. It only acquired its plural form in America during the late 19th century.