The phrase assumes that a living is something you must earn, not something you have.
The English word earn derives from the Old English earnian, meaning to labor for, to deserve, to merit through effort.1 The word living, in the sense of a means of maintaining life, appeared in Middle English by the fourteenth century. Together, "earning a living" became one of the foundational phrases of the English-speaking relationship with work: the idea that sustenance is not a given but a reward for effort.
The phrase contains an assumption so familiar that it is nearly invisible. To earn a living implies that a living, the ability to survive, must be purchased through labor. It frames existence itself as conditional on productivity. Other languages organize the concept differently. The French gagner sa vie (to win one's life) frames it as a contest. The German seinen Lebensunterhalt verdienen (to deserve one's life-support) emphasizes merit.2
For most of human history, the distinction between working and living did not exist in the way the phrase implies. In subsistence economies, work was not separate from life but embedded in it: planting, harvesting, cooking, building, all woven into the fabric of daily existence.3 The concept of earning a living required a prior separation, the creation of labor as something distinct from the rest of experience, exchangeable for wages, which could then be exchanged for the necessities of life.
The phrase became naturalized during the Industrial Revolution, when wage labor replaced subsistence as the dominant mode of survival for the majority of the population in industrializing countries.4