Origins
The English word "week" descends from Old English wicu (also wice or wucu, depending on dialect), a feminine noun meaning both a period of seven days and, in its older sense, a turning or change. The word traces back through Proto-Germanic *wikō to the Proto-Indo-European root *weik-, meaning "to bend" or "to wind." The underlying metaphor is one of turning or cycling — the week as a recurring sequence that bends back upon itself.
The Germanic cognates confirm the reconstruction: German Woche, Dutch week, Swedish vecka, Danish uge (with sound changes obscuring the relationship somewhat), Icelandic vika, and Gothic wiko. All refer to a seven-day period. The Gothic form is attested in Wulfila's 4th-century Bible translation, confirming that the seven-day week was established among the Germanic peoples by late antiquity.
The seven-day week itself is not a natural astronomical unit in the way that the day, month, and year are. Its origins lie in the ancient Near East. The Babylonians observed a seven-day cycle loosely tied to the phases of the moon (roughly a quarter of a lunation), and the Jewish tradition enshrined it in the biblical account of creation and the Sabbath. The Romans adopted the seven-day planetary week — with days named after the Sun, Moon, Mars, Mercury, Jupiter, Venus, and Saturn — by the 1st century CE, and it spread throughout the Empire.
Proto-Indo-European Roots
The Germanic peoples encountered the Roman planetary week and adopted its structure, but characteristically translated the Roman god-names into their own pantheon. This is why English has Sunday (Sun's day), Monday (Moon's day), Tuesday (Tiw's day, for the war god equivalent to Mars), Wednesday (Woden's day, for Mercury), Thursday (Thunor's day, for Jupiter), Friday (Frig's day, for Venus), and Saturday (which retained the Roman Saturn). The word for the seven-day cycle itself, however, was native Germanic — *wikō was not borrowed from Latin septimana or any Romance form.
In Old English, the word wicu appeared in numerous legal, religious, and everyday contexts. The Anglo-Saxon church organized its liturgical calendar by weeks, and legal codes specified fines and obligations in terms of weeks. The compound sennight (from seofon nihta, "seven nights") was used interchangeably with wicu in some contexts, reflecting the older Germanic habit of reckoning time by nights.
The semantic range of the PIE root *weik- extended beyond time-reckoning. In Latin, the related form vicis meant "change, alternation, turn" (surviving in English "vicissitude" and the prefix "vice-" meaning "in place of"). This connection illuminates the original Germanic conception: the week was not simply a count of seven days but a turning, a regular alternation in the rhythm of life — perhaps originally tied to market days, religious observances, or agricultural routines that recurred in a fixed cycle.
Middle English
The modern compound "weekend" is surprisingly recent, first attested in 1879 in a British publication. The concept of a two-day weekend is largely a product of industrial labor negotiations in the 19th and 20th centuries. "Weekday" is older, attested from the 14th century. The adjective "weekly" dates to the 15th century.
The week remains one of the most culturally entrenched units of time in the modern world, organizing work, worship, and rest across virtually all societies. The English word for it quietly preserves, in its etymology, the ancient metaphor of cyclical turning that gave the concept its name among the Germanic peoples over two thousand years ago.