Why do we "beat seven bells out of" someone?

To thrash someone within an inch of his life is sometimes referred to has beating seven bells out of him. But why should seven be the number chosen? This source here acknowledges the phrase exists but is silent as to the etymology, and here the phrase appears as kick seven bells... and alternatively ten bells, which I have never come across.

I've heard it suggested that the term derives from seven bells, the nautical expression for half-an-hour before the end of the watch (so one would beat someone within a small space of the end of his life). But how do we reconcile that with the alternative beat seven shades (of shit) out of?

Solution 1:

It was answered on Ask.Metafilter:

Like danb indicates, it's nautical slang. A four hour watch consists of eight half hour bells - seven bells is almost all the way.

The OED: "In Naut. slang phrs. to knock seven bells out of (someone): to beat (someone) severely; similarly, to scare seven bells out of: to terrify."

Edit: the earliest reference I found is Na motu: or, Reef-rovings in the South seas by Edward T. Perkins in 1854:

"I suppose there were a hundred look-outs between the night-heads, does that give you any right to disobey orders? My orders are, that no man shall sleep on watch. I'da mind, when I first began, to make an example of you ; but bear it in mind, that if I ever catch you at it again, I'll knock seven bells out of you ! Go ' long ; I've done with you."

There are a lot nautical references from the 19th century. Wikipedia has a good article on the eight ship's bells.

Edit 2: The Royal Navy's guide to Navy slang says:

To Knock Seven Bells out of a Man

An old naval expression for the giving of a sound thrashing (the nautical equivalent of "Knocking a man for six" [a cricketing term]); presumably to knock all eight bells out of a man would be to kill him!

Edit 3: "seven shades of" is much more recent. Here are some of the earliest references I found:

• W. T. Tyler's 1982 Rogue's March: "kick seven shades of shit"
• W. L. Ed Webb's 1985 The Bedside Guardian 34: "Does thou want seven shades of shit kicked out of thee?"
• June 1989 SPIN magazine: "kicked up seven shades of hell"
• 1994 British journal of photography: Volume 141: "beat seven shades [of hell]"
• Robin Jarvis's 2010 Dancing Jax: "He'd best hope the police find him before I do because I will personally kick seven shades out of him."

Solution 2:

Seven is just a magical number, and so has been used for many things since antiquity. We have seven days in a week, seven is the number of the sum of any two opposite sides of a die, there are seven deadly sins, etc.

The number seven is well-exercised in Christianity:

• The Seven Corporal Acts of Mercy and Seven Spiritual Acts of Mercy of Roman Catholic, Anglican, and other traditions
• The Seven deadly sins: lust, gluttony, greed, sloth, wrath, envy, and pride
• Seven Gifts of the Holy Spirit
• The Seven Joys of the Virgin Mary, of Roman Catholic, Anglican, and other traditions
• The Seven Sacraments in the Catholic faith (though some traditions assign a different number)
• The Seven Sorrows of the Virgin Mary, of Roman Catholic, Anglican, and other traditions
• There are seven suicides mentioned in the Bible (OT and NT).[5]
• The seven terraces of Mount Purgatory (one per deadly sin)
• The Seven Virtues: chastity, temperance, charity, diligence, kindness, patience, and humility
• In the genealogy in the Gospel of Luke, Jesus is 77th in a direct line
• The number of heads of the three beasts (7 × 10 × 7 + 7 × 10 × 10 + 7 × 10 = 1260) of the - - Book of Revelation, and of some other monsters, like the hydra and the number of seals

[Wikipedia]

But other religions and cultures reserve special significance for the number as well. It is "a highly symbolic number in the Torah, alluding to the infusion of spirituality and Godliness into the creation," and "the Seven Lucky Gods refer to the seven gods of good fortune in Japanese mythology."

[Ibid.]

There is too much more to list here.