Hot rods are typically old, classic American cars with large engines modified for linear speed. The origin of the term "hot rod" is unclear. A possible origin includes replacement of the camshaft with a new ("hotter") version, sometimes known as a hot stick or hot rod. Roadsters were the cars of choice because they were light, easy to modify, and inexpensive. The term became commonplace in the 1930s or 1940s as the name of a car that had been "hopped up" by modifying the engine for higher performance. A term common in the early days was "gow job". This has fallen into disuse except with historians. The term has broadened to apply to other items that are modified for a particular purpose, such as "hot-rodded amplifier".