stress (n.)

c. 1300, stresse, "hardship, adversity; constraining or compelling force or pressure, coercion;" the original senses are mostly archaic or obsolete. The word is in part a shortening of distress (n.) and in part from Old French estrece "narrowness, oppression," from Vulgar Latin *strictia, from Latin strictus "tight, compressed, drawn together," past participle of stringere "draw tight" (see strain (v.)).

The meaning "physical strain on a material object" is from mid-15c. In mechanics, "force acting on or within a body and tending to deform it," by 1855 (Rankine), but by others confused at the start with pressure, strain, and deformation.

In this paper the word strain will be used to denote the change of volume and figure constituting the deviation of a molecule of a solid from that condition which it preserves when free from the action of external forces ; and the word stress will be used to denote the force, or combination of forces, which such a molecule exerts in tending to recover its free condition, and which, for a state of equilibrium, is equal and opposite to the combination of external forces applied to it. [William John MacQuorn Rankine, "On Axes of Elasticity and Crystalline Forms," 1855]

The figurative meaning "weight, importance, emphasis" is by 1650s, perhaps from notion of "a testing strain, pressure put on something by relying on it." In reference to the relative loudness of vocal utterance of words or syllables, by 1749. The purely psychological sense in reference to a cause of anxiety is attested by 1955.

c. 1300, stressen, "to subject (someone) to force or compulsion; restrain, confine," senses now obsolete, a short form of distress (v.), or else of Old French estrecier, estrescer, from Vulgar Latin *strictiare, from Latin stringere "draw tight," which also is the source of stress (n.).

In mechanics, "subject (a thing) to physical stress," by 1540s; psychological sense of "subject (a person) to mental or emotional stress" is by 1973. The figurative meaning "put emphasis on" is recorded by 1896, perhaps from notion of laying pressure on something by relying on it. Related: Stressed; stressing.