A bouquet garni is simply a bundle of herbs. The traditional implementation involves placing the herbs into a cheesecloth bag and tying them up, but the bag not essential; the term refers simply to the herb.
The first use of the bouquet garni has been lost to history, but the first mention of it is in The Oxford Companion to Food first published in 1999. It described the use of the bouquet garni as a tool for masking the flavor of different foods during the Middle Ages. During the 1600s, French and English cooks began using herbs more precisely to create subtle flavor combinations.
By this point, the use of herb bundles was already an established cooking technique; however, the components varied. In 1656, Pierre de Lune described a bundle consisting of thyme and chervil along with parsley. He wrapped his herbs in bacon.