The term tramper is derived from the British meaning of "tramp" as itinerant beggar or vagrant; in this context it is first documented in the 1880s, along with "ocean tramp" (at the time many sailing vessels engaged in irregular trade as well).
The tramp trade first took off in England around the mid 19th century. The dependability and timeliness of steam ships was found to be more cost-effective than sail. Coal was needed for ships' boilers, and the demand created a business opportunity for moving large amounts of best Welsh coal to various seaports in England. Within a few years tramp ships became the workhorses of trade, transporting coal and finished products from English cities to the rest of the world.
The size of tramp ships remained relatively constant from 1900 to 1940, at about 7,000 to 10,000 deadweight tons (dwt.). During World War II, the United States created the Liberty Ship; a single design that could be used to carry just about anything, which weighed in at 10,500 dwt. The U.S. produced 2708 Liberty Ships and they were used on every international trade route. After World War II, economies of scale took over and the size of tramp ships exploded to keep up with a booming supply and demand cycle. During this time the bulk carrier became the tramp of choice for many owners and operators. The bulk carrier was designed to carry coal, grain, and ore, which gave it more flexibility and could service more ports than some of its ancestors, which only carried a single commodity.
Today the tramp trade includes all types of vessels, from bulk carriers to tankers. Each can be used for a specific market, or ships can be combined like the oil, bulk, ore carriers to accommodate many different markets depending where the ship is located and the supply and demand of the area. Tramp ships often carry with them their own gear (booms, cranes, derricks) in case the next port lacks the proper equipment for loading or discharging cargo.