We generally use the word "stress" when we feel that everything seems to have become too much, we are overloaded. We are all familiar with how it feels. Few however, know what it is exactly, where it comes from, and —especially— why we call it that way.
The word “Stress” originates from the Old French estrece, meaning "narrowness, oppression," from Vulgar Latin strictia, and from Latin stringere: "tight, compressed, drawn together, draw tight."
This seems especially apt, taken into account that stress triggers blood vessels to close, thereby reducing profuse bleeding from a flesh wound. Reaction to stress also makes the blood thicker and more viscous.
The term "stress" had none of its contemporary connotations before the 1920s. However, the word had long been in use in physics. The physical sciences, most notably engineering, used terms like stress, strain, resilience, pressure, or elasticity to describe the effects of materials.
In physics, Stress describes the force that produces strain on a physical body (i.e.: bending a piece of metal until it snaps occurs because of the force, or stress, exerted on it).
In the 1920s and '30s, biological and psychological circles slowly started to use the term to refer to a mental strain or to a harmful environmental agent that could cause illness.
The most important figure to borrow the term from the field of physics and to use it in its contemporary meaning was Hans Selye. But it didn’t start with him. We have to go back, to the introduction of the concept of a bodily balance.
A key to the understanding of stress is the concept of milieu interieur. This is the internal environment of the body and was first advanced by the French physiologist Claude Bernard. In this concept, he described the principles of dynamic equilibrium.
In dynamic equilibrium, a constant and steady balance in the internal bodily environment, is essential to survival. Some external forces —such as temperature, oxygen concentration in the air, the expenditure of energy, and the presence of predators— can change and threaten the internal balance. The body must react and and compensate to restore the balance. Diseases are also stressors that threaten the constancy of the Milieu Interieur.
The neurologist Walter Cannon coined the term homeostasis to further define the dynamic equilibrium that Bernard had described. He also was the first credited with recognising that stressors could be emotional, as well as physical. Through his experiments, he demonstrated the "fight or flight" response that man and other animals share when threatened.
Cannon traced these reactions to the release of powerful neurotransmitters from a part of the adrenal gland, the medulla. Neurotransmitters are the body's chemicals that carry messages to and from the nerves. The adrenal medulla secretes two neurotransmitters, epinephrine (also called adrenaline) and norepinephrine (noradrenaline), in the response to stress. The release of these neurotransmitters leads to the physiologic effects seen in the fight or flight response, for example, a rapid heart rate, and increased alertness.
Hans Selye began using the term stress after completing his medical training at the University of Montreal in the 1920’s. He noticed that no matter what his hospitalised patients suffered from, they all had one thing in common. They all looked sick. In his view, they all were under physical stress.
Selye took Cannon’s observations about Homeostasis one step further. In his experiments, Selye induced stress in rats in a variety of ways. He found typical and constant psychological and physical responses to the adverse situations that were imposed on laboratory rats. He exposed rats to stress and discovered adaptive processes to adjust to new external factors and restore the “Milieu Interieur” or “Homeostasis.” These processes are healthy, appropriate adjustment mechanisms. However, if they were excessive, could damage the body and become much like illness.
This observations were the beginning of an understanding of stress as a balancing act of the body, why stress can be harmful, and why the word stress has earned such a bad name.