Did people ever use the word "cock" as a euphemism for "God"?

English has a lot of surprises.

When I was checking the etymology of "cocksure", I found this entry in Oxford Dictionaries:

1 British A male bird, especially of a domestic fowl.

Below is another definition from "An Etymological Dictionary of Modern English" By Ernest Weekley (originally published in 1921):

Moreover:

By cock and pie: an adjuration equivalent to "by God and the service book."

Questions:

• How in the world is/was cock a euphemism for God? And how is it related with God?
• Are there any references to this in the current vernacular?
• Are there any connotations to vulgarism also?

Solution 1:

There are a few sources of this online, but none give anything more drilled down than the ones you've already quoted.

While skeptically allowing that they may all be working from the same flawed sources, the logic seems to be this:

Cocksure, cocks wounds, etc. were oaths and phrases from a time when using the word God was serious blasphemy. But, basically, the word cock really seems to have meant God (at least to some people).

It appears to merely be a stand-in word: a minced oath. Much in the way people say "Oh my goodness", instead of "Oh my god", to avoid blasphemy.

Here is an excerpt from Swearing: A Social History of Foul Language, Oaths, and Profanity in English, by Geoffrey Hughes:

Seeing the context in Shakespeare pretty much nails it for me.

Solution 2:

Yes, people did use the word “cock” as a euphemism for “God”, but it's now obsolete.

Reverend Alexander Dyce, the literary historian and Shakespeare biographer wrote in The Works of William Shakespeare, Volume 9 (1867):

cock, a corruption of, or euphemism for God : Cock's passion, iii. 152; By cock vii. 181. (This irreverent alteration of the sacred name was formerly very common : it occurs at least a dozen times in Heywood's Edward the Fourth, where one passage is

"Herald. Sweare on this booke, King Lewis, so help you God, You meane no otherwise then you haue said. King Lewis. So helpe me Cock as I dissemble not."

Part ii. sig. N. 4 ed. 1619)

cock and pie -- By i. 352, iv 387. A not uncommon oath, of uncertain derivation : cock has been understood to be the corruption of God (see above) and pie to mean the service book of the Romish Church ; which seems much more probable than Douce's supposition that this oath was connected with the making of solemn vows by knights in the days of chivalry during entertainments at which a roasted peacock was served up.

The Concise New Partridge Dictionary of Slang and Unconventional English (2007) by Terry Victor and Tom Dalzell says:

cock-almighty noun the best. Obsolete euphemism of 'cock' for 'God', hence 'God almighty', with reference to more modern nuances of cock (chief, man, etc.)