I have long been interested in the evolution of words as their meanings change and in his book The Scientific Revolution (1996), author Steven Shapin makes some interesting observations and speculations about two words that over time came to mean things almost directly opposite to what they had meant before. One such word is ‘revolution’.

From antiquity through the early modern period, a “revolution” invoked the idea of a periodically recurring cycle. In Copernicus’s new astronomy of the mid sixteenth century, for example, the planets completed their revolutions round the sun, while references to political revolutions gestured at the notion of ebbs and flows or cycles – fortune’s wheel – in human affairs. The idea of a revolution as a radical and irreversible reordering developed together with linear, unidirectional conceptions of time. In this newer conception revolution was not recurrence but its reverse, the bringing about of a new state of affairs that the world had never witnessed before and might never witness again. Not only this notion of revolution but also the beginnings of an idea of revolution in science date from the eighteenth-century writings of French Enlightenment philosophers who liked to portray themselves, and their disciplines, s radical subverters of ancien regime culture. (Some of the seventeenth-century writers this book is concerned with saw themselves not as bringing about totally new states of affairs but as restoring or purifying old ones.) The notion of revolution as epochal and irreversible change, it is possible, was first applied in a systematic way to events in science and only later to political events. (p. 3)

Another word whose meaning changed though not as dramatically is ‘probable’.

It was about this time that there was a notable shift in the meaning of the word “probable.” Before the seventeenth century, to say that a claim was probable was to indicate that it was well attested, for instance, by Aristotle or other recognized authorities (as in our present-day sense of “probity”). By about the middle of the seventeenth century “probability” acquired a new meaning indicating an adequate degree of evidential support for a claim that was not certainly true. (p. 101)