Hot rods are typically American cars with large engines modified for linear speed.
The origin of the term “hot rod” is unclear. One explanation is that the term is a contraction of “hot roadster,” meaning a roadster that was modified for speed. Another possible origin includes modifications to or replacement of the camshaft(s), sometimes known as a “stick” or “rod”. A camshaft designed to produce more power is sometimes called a “hot stick” or a “hot rod”. Roadsters were the cars of choice because they were light. The term became commonplace in the 1930s or 1940s as the name of a car that had been “hopped up” by modifying the engine in various ways to achieve higher performance. A term that was common in the early days to refer to a hot rod was a “gow job”. This has fallen into total disuse except with historians.
The term can also apply to other items that are “souped up” for a particular purpose, such as “hot-rodded amplifier”.