The word "workout" is a modern English compound formed from the native Germanic elements "work" and "out." Its formation follows a common pattern in English where a verb-particle combination ("to work out") is nominalized into a single noun. The literal sense is of "working something out to completion," which evolved from the general meaning of solving a problem through effort to the specific modern meanings. The primary contemporary sense of a physical exercise session emerged in the mid-20th century, applying the logic of thoroughly exerting the body to achieve a result, paralleling the older sense of a trial or test to determine effectiveness.

Structure: work + out - work: From Old English weorc, meaning "something done, action, deed, labor." In this compound, it carries the sense of physical or mental effort. - out: From Old English ūt, meaning "out, outside, forth." In this compound, it functions as an adverbial particle indicating completion, thoroughness, or a result.