E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
(Greek, hepta; Latin, septem; German, sieben; Anglo-Saxon, seofan; etc.). A holy number. There are seven days in creation, seven spirits before the throne of God, seven days in the week, seven graces, seven divisions in the Lords Prayer, seven ages in the life of man, and the just fall seven times a day. There are seven phases of the moon, every seventh year was sabbatical, and seven times seven years was the jubilee. The three great Jewish feasts lasted seven days, and between the first and second of these feasts were seven weeks. Levitical purifications lasted seven days. We have seven churches of Asia, seven candlesticks, seven stars, seven trumpets, seven spirits before the throne of God, seven horns, the Lamb has seven eyes, ten times seven Israelites go to Egypt, the exile lasts the same number of years, and there were ten times seven elders. Pharaoh in his dream saw seven kine and seven ears of corn, etc.
It is frequently used indefinitely to signify a long time, or a great many; thus in the Interlude of the Four Elements, the dance of Apetyte is called the best that I have seen this seven yere. Shakespeare talks of a man being a vile thief this seven year.