Origin of "blimey"
The OED entry goes for either blind me or blame me.
Vulgar corruption of the imprecation blind me! or blame me! (blame v. 7a). (Cf. gorblimey int.)>
1889 in A. Barrère & C. G. Leland Dict. Slang s.v.
1894 Punch 27 Oct. 193/1 Blymy, you're a knockout!
1897 W. S. Maugham Liza of Lambeth ix. 153 Bli' me if I know wot yer all talkin' abaht.
1922 J. Joyce Ulysses ii. xii. [Cyclops] 297 God blimey if she aint a clinker... Blimey it makes me kind of bleeding cry.
1932 Punch Almanack 1933 7 Nov. [18/1] ‘Your mentality is erroneous and—er—soggy. Blime! what a cod!’ he concluded.
1954 ‘R. Crompton’ William & Moon Rocket viii. 235 ‘Blimey!’ said Charlemagne. ‘Pardon him, dear,’ said Miss Milton in a shaking voice. ‘He doesn't often use bad language.’
And for Gorblimey
Vulgar corruption of the imprecation God blind me! See also quots. 1919, 1925.>
1896 A. Morrison Child of Jago i. 16 Gawblimy, not what?
1909 J. R. Ware Passing Eng. Gorblimy (about 1875). A gutter phrase.
1911 L. Stone Jonah i. ix. 105 ‘Gorblimey! A knock-out!’..Stinky, with a haphazard blow, had given Chook the dreaded knock-out.
1914 T. A. Baggs Back from Front xix. 92 Gor blimey, 'ow are ye, then, old townie?
1915 A. D. Gillespie Let. 27 Mar. in Lett. from Flanders (1916) 74
Most of the infantry now wear the soft ‘Gor'bli'me’ hat which looks horrid, but does not give such a mark as the flat-topped ‘Brodrick’.1918 W. J. Locke Rough Road v. 51 ‘Gorblime!’ said Chipmunk, ‘that's the first I 'eard of it.’
1919 War Terms in Athenæum 8 Aug. 729/1 ‘Gor-blimey’, a soft service cap.
1925 E. Fraser & J. Gibbons Soldier & Sailor Words Gorblimey... An exclamation or adjective of emphasis. A ‘Gorblimey’ was the common colloquial term for an unwired, floppy, field-service cap worn by a certain type of subaltern in defiance of the Dress Regulations. Lines from a song, popular before the War, ran:—‘He wears Gorblimey trousers An a little Gorblimey 'at.’
1956 J. Masters Bugles & Tiger 49 A tweed gorblimey cap worn well forward on the head.
1958 Oxf. Mag. 27 Feb. 326/1 The British and American tendency is to emphasise the Gorblimey aspect of history, the feelings of the ordinary man on the spot at the time.
1962 Listener 31 May 967/1 She offered a gorblimey cheerfulness.
This is an example of the so-called subjunctive in English. Such sentences are invocations where the act of saying them is presented as an exhortation that will make them hopefully occur. Here are some similar examples:
- God save the queen.
- Peace be upon you.
- Bless you.
- Praise be.
- Well strike me down with a thunderbolt.
- Heaven forbid.
- So be it.
- (God) damn you.
Sometimes, of course, these sentences don't really convey that we actually do want these things to happen. They are very often just an expression of surprise:
- Well strike me down with a thunderbolt.
- God blind me.
- Shiver me timbers.
In such sentences we don't really think that the speaker wants to be struck down by a thunderbolt, blinded, or have their boat hit by a cannon so hard that its timbers shivered.
So, as to where cor blimey comes from, if it comes from God blind me, it would seem to be a relatively transparent saying.
However, the purpose of my post is to show why we might have ended up with cor blimey from god blind me.
First of all, the (admittedly modern) transcription for God blind me in RP is:
- gɒd blaɪnd mi
You will notice that there's a /d/ there at the end of the word blind. Interestingly, the phoneme /d/ is subject to elision in English if surrounded by consonants and occurring after a voiced consonant. Here it's followed by an /m/ and preceded by a voiced /n/. So in natural speech, this consonant would more often than not be dropped, giving us:
- gɒd blaɪn mi (God bline me)
What we see, after the /d/ has been dropped, is an /n/ followed by an /m/. Now, the phoneme /n/ is also highly unstable in English. It tends to change its place of articulation according to the following consonant. For this reason we see words like input being pronounced imput and so forth. This is called anticipatory assimilation and in this instance, if people say the phrase above in natural speech, this is going to give us:
- gɒd blaɪm mi (God blime me)
Looking at the word God, you will notice that this too ends in a /d/. However, it is not surrounded by consonants. The phoneme /d/ as we have already seen is unstable. When it doesn't disappear, it also likes to change place according to the following consonant. So in natural speech we get things like bab boy for bad boy or Rebbridge for Redbridge. Again this is an example of anticipatory assimilation. In our current example this will now give us:
- gɒb blaɪm mi
Because we have a sequence of two /b/s and then two /n/s, each of these double consonant segments are very likely to be interpreted as a single consonant:
- gɒ blaɪmi
Now, if we are interpreting the /b/ as being part of the second word, we are going to interpret the 'O' sound from god as being an /ɔ:/ as in THOUGHT, not an /ɒ/ as in LOT. The reason for this is that word final English syllables are not allowed to end in /ɒ/. The THOUGHT vowel is the nearest allowable vowel to the original LOT vowel that we can use in a word final syllable.
So, there's some phonetic and phonological speculation about why cor blimey may be derived from God blind me. Of course whether this actually is the derivation in the first place, we don't truthfully know.
I am well aware that this does not exactly answer the Original Poster's question - but it was too long to put in the comments!