Origins
The English word 'pressure' entered the language in the late fourteenth century, from Old French 'pressure,' which descended from Latin 'pressura' (a pressing, a squeezing, oppression). The Latin noun is formed from 'pressus,' the past participle of 'premere' (to press), with the abstract noun suffix '-ura,' which indicates a state, condition, or result of an action.
Unlike the verb compounds built on 'premere' — compress, depress, express, impress, oppress, repress, suppress — which each specify a direction of pressing through their prefix, 'pressure' is directionless. It names the force itself, the raw phenomenon of pressing, without specifying whether the pressing is upward, downward, inward, or outward. This generality has made it one of the most versatile words in the language.
The earliest English uses were concrete and bodily: the pressure of a hand on a wound, the pressure of a crowd, the pressure of tight clothing. From there the word expanded rapidly into metaphor. By the fifteenth century, 'pressure' described mental and emotional stress — the feeling of being pressed upon by circumstances, obligations, or fears. By the seventeenth century, it described social and political coercion — bringing pressure to bear on someone to change their behavior.
Scientific Usage
The scientific meaning transformed the word's importance. In the seventeenth century, natural philosophers began measuring and quantifying pressure as a physical property. Evangelista Torricelli invented the barometer in 1643, measuring atmospheric pressure — the weight of the column of air above the Earth's surface pressing down. Blaise Pascal demonstrated in the 1640s and 1650s that pressure applied to a confined fluid is transmitted equally in all directions (Pascal's Law), the foundation of hydraulics. Robert Boyle established in 1662 that the pressure and volume of a gas are inversely proportional (Boyle's Law).
These discoveries made 'pressure' a fundamental term of physics. In modern science, pressure is defined as force per unit area (P = F/A). The SI unit of pressure is the pascal (Pa), named after Blaise Pascal. Standard atmospheric pressure at sea level is approximately 101,325 pascals, or about 14.7 pounds per square inch. Blood pressure, tire pressure, water pressure, air pressure — in each case, the word retains its Latin core: the force exerted by pressing.
The verb 'to pressure' (to apply pressure to someone, to coerce) is a relatively recent development, first attested in the early twentieth century and originally considered informal. 'Pressurize' (to maintain artificially high air pressure, as in an aircraft cabin) dates to the 1940s, when commercial aviation made it necessary to pressurize cabins at high altitudes. 'Peer pressure' (the social force exerted by one's age group) became a common term in the 1960s and 1970s.
Figurative Development
The compound 'blood pressure' entered medical vocabulary in the mid-nineteenth century. High blood pressure (hypertension) and low blood pressure (hypotension) are among the most commonly measured health indicators worldwide. 'Under pressure' — both as a technical term (a container under pressure) and as an emotional expression (a person under pressure) — demonstrates the word's dual life as both scientific terminology and everyday metaphor.
The German word 'Druck' (pressure, from 'drücken,' to press) is a semantic parallel rather than a cognate — a different Germanic verb that independently developed the same concrete-to-abstract journey. Similarly, 'Druck' means both 'pressure' and 'printing' in German, paralleling the English connection between 'press' (to apply force) and 'press' (a printing machine).
'Pressure' occupies a unique position in the 'premere' family: it is the noun that names what all the verbs do. Compress, depress, express, impress, oppress, repress, and suppress are all specific modes of applying pressure. The word is their common denominator, the undirected force that each prefix channels into a particular direction and meaning.