A pea coat refers to a heavy double-breasted outer coat, usually made from thick wool, which uses two rows of large buttons as closures. Those issued by the U.S. Navy used buttons with an anchor emblem.
The origin story of the pea coat favored by the U.S. Navy dates back to 1723, when sailors would wear heavy coats made from a material known as pilot cloth, or P-cloth for short. This resulted in the coats being referred to as p-coats. Coats constructed of this material were worn during cold and generally miserable weather. The name eventually came to mean coats worn for "Pea Soup" weather, hence the difference in spelling. While this account of the coat's history is likely true, Danish and British sailors were also known to wear a device called a "pijjekker". Pij refers to the type of cloth used, while jekker is a Danish word for coat or jacket. The cloth itself was coarse, heavy and bore its nap on one side. The image of a sailor in a pea coat eventually became widely recognizable, making the cold weather gear closely associated with naval personnel from all countries. While pilot cloth or pij fabric are no longer used, the basic shape and appearance of the pea coat has changed very little otherwise.