Origins
The English word 'clock' is, at its core, a word for a bell. It entered Middle English as 'clokke' in the fourteenth century, borrowed either from Middle Dutch 'clocke' or from Old North French 'cloque,' both meaning 'bell.' These derive from Medieval Latin 'clocca,' which is widely believed to be a loanword from an insular Celtic language — Old Irish 'cloc' or a related Brythonic form. The Celtic origin is supported by the word's early attestation in Irish monastic Latin, where it referred to the bells that regulated the daily rhythm of prayer in monasteries.
The semantic shift from 'bell' to 'timekeeping device' is one of the most famous in English etymology, and it reflects a genuine revolution in technology. Before mechanical clocks, time in medieval Europe was kept by sundials, water clocks, and hourglasses. The earliest mechanical clocks, appearing in European monasteries and cathedral towers in the late thirteenth century, were essentially bell-striking mechanisms — escapement-driven devices that released a hammer to strike a bell at regular intervals. These clocks had no dials, no hands, and no visual display. They were purely auditory: you heard the time, you did not see it. The word 'clock,' meaning 'bell,' thus transferred naturally to the machine that rang it.
The spread of the word across European languages confirms this bell-origin. French 'cloche' means 'bell' (and by extension, a bell-shaped hat or glass cover). German 'Glocke' means 'bell' — the clock itself is 'Uhr' (from Latin 'hora'). Dutch 'klok' means both 'bell' and 'clock.' Swedish 'klocka' likewise means both. In each language, the semantic relationship between bell and timepiece is preserved to varying degrees.
Development
The first reliable mechanical clocks appeared in Italy and England in the late thirteenth century. The Dunstable Priory clock of 1283 is often cited as the first documented clock in England. Salisbury Cathedral's clock mechanism, dating to approximately 1386, is one of the oldest surviving working clock mechanisms in the world. These early tower clocks were massive iron constructions driven by falling weights, with a verge-and-foliot escapement that regulated the rate at which the weights descended. Their accuracy was poor by modern standards — they could drift by as much as fifteen minutes per day — but they transformed urban life by imposing a shared, public time on communities that had previously relied on variable natural indicators.
The addition of clock faces with hour hands came in the fourteenth century, and minute hands did not become standard until the late seventeenth century, after the invention of the pendulum clock by Christiaan Huygens in 1656 made timekeeping accurate enough for minute-resolution to matter. The second hand followed shortly after. Each of these innovations moved the clock further from its bell-origins toward a visual instrument, but the name — the bell-word — persisted.
In English, the word has generated a rich family of derivatives. 'Clockwise' (in the direction of a clock's hands) dates from the mid-nineteenth century and replaced the older term 'sunwise.' 'Clockwork' (a mechanism driven by springs and gears) dates from the seventeenth century; 'like clockwork' (with perfect regularity) is attested from 1710. 'O'clock' is a contraction of 'of the clock,' distinguishing clock time from other methods of telling time (such as sundial time). 'To clock in' and 'to clock out' (to register arrival at and departure from work) date from the late nineteenth century, when time clocks were introduced in factories.
Figurative Development
The expression 'to clean someone's clock' (to strike or defeat them decisively) is American slang from the mid-twentieth century, possibly from the idea of hitting someone in the face (the 'clock' being slang for a face, perhaps because clock faces resemble human faces). 'To turn back the clock' (to return to an earlier state) draws on the visual metaphor of reversing the hands.
The Celtic origin of 'clocca' is itself significant in the history of European languages. It is one of a small number of Celtic loanwords that achieved pan-European distribution through Latin, reflecting the importance of Irish and British monasticism in the early medieval period. Irish monks, who established monasteries from Iona to Bobbio, carried their bell-regulated monastic schedule — and the word for the bell that governed it — across the continent. The humble monastery bell thus gave its name to one of the most consequential inventions in human history.