The word 'epoch' entered English in the early seventeenth century from Medieval Latin 'epocha,' from Greek 'epokhḗ' (ἐποχή), meaning 'a stoppage,' 'a fixed point,' 'a star's position at a given moment,' and by extension 'a point in time from which subsequent events are reckoned.' The Greek word comes from 'epékhein' (to hold upon, to pause, to check, to stop), composed of 'epí' (upon, at) and 'ékhein' (to hold, to have, to be in a state). The PIE root behind 'ékhein' is *seǵʰ- (to hold).
The original astronomical meaning is revealing. In Greek astronomy, an 'epokhḗ' was the position of a celestial body at a specific moment in time — a 'held' position from which its future movement could be calculated. This is still the technical meaning in astronomy: the epoch of an orbit is the reference time at which the orbital elements are defined. The metaphor extends naturally to chronology: an epoch is a held moment, a stake driven into the flow of time, from which other events are measured forward or backward.
The philosophical meaning of 'epoché' (suspension of judgment) developed among the ancient Greek Skeptics, particularly Pyrrho of Elis and his followers. The Pyrrhonist epoché meant refusing to commit to any belief about how things really are — 'holding back' from judgment in order to achieve ataraxia (tranquility). Sextus Empiricus, in his 'Outlines of Pyrrhonism,' described epoché as the balance point where equally strong arguments for and against a proposition produce a suspension of belief.
Edmund Husserl revived the concept in the twentieth century as the cornerstone of phenomenological method. The 'phenomenological epoché' or 'bracketing' involves suspending the natural attitude — the everyday assumption that the world exists independently of our experience of it — in order to examine consciousness itself. This philosophical sense of 'epoch' (a holding-back) is related to but distinct from the chronological sense (a held point in time): both involve a kind of pause, a suspension of the normal flow.
In geology, 'epoch' has a precise technical position in the hierarchical time scale. The hierarchy descends: eon, era, period, epoch, age. The current epoch is the Holocene (beginning c. 11,700 years ago), though there is ongoing scientific debate about whether we have entered a new 'Anthropocene' epoch defined by human impact on the Earth's geology and ecosystems. An epoch in geology spans millions to tens
In computing, the 'Unix epoch' is January 1, 1970, at 00:00:00 UTC — the fixed point from which Unix systems count time in seconds. This technical usage is perfectly faithful to the word's original meaning: a fixed, held point from which all other times are reckoned.
The adjective 'epoch-making' or 'epochal' describes events so significant that they mark the boundary between one period and another — events that create a new epoch. The French Revolution, the invention of the printing press, the splitting of the atom — these are 'epochal' events, moments where time seems to pause and restart with a new character. The word 'epoch' gives English a precise term for this concept: not just a notable event, but an event that resets the clock.