An Etymological Dictionary of Astronomy and Astrophysics

A division of time containing 7 successive days, which is completely independent of the month or the year. Unlike the month and the year, the week is an artificial unit of time, lacking an equivalent astronomical period.

Etymology (EN): M.E. weke; O.E. wice, cf. O.N. vika, M.Du. weke, O.H.G. wecha, Ger. Woche, akin to L. vicis “turn, change.”

Etymology (PE): Hafté “week, hebdomad,” from haft “seven” → hepta-.