If the acronym came from Al Murray’s work and some posters have adopted it, then it amounts to little more than a bit of group slang here and a strange bit of linguistic flourish on his behalf. Further, it isn’t particularly accurate to the era, when as has been said, it was not used whatsoever.
The Dominions under the 1920s evolution of the Empire were Canada, Newfoundland, South Africa, NZ and Australia. Of those, the term ‘Dominion’ is most closely associated with Canada, with the others employing it in a technical manner when referring to specific relationships with Britain.
I would further note that the terms ‘Britain’ and ‘British’ were used quite more often than ‘UK’ and ‘United Kingdom’ in popular discourse and press usage, official documentation and both primary and secondary sources of the era. Whilst the declarations of war refer to ‘His Majesty’s Government in the United Kingdom’, this was more of the exception which we might see as being the formal/diplomatic full name rather than what would actually be used by the likes of Mr. Churchill.
The use of ‘British Empire’ and ‘Imperial’ was not quite as prevalent as in WW1, but wasn’t completely unheard of. The middle position of ‘British Commonwealth’ did see a lot more use in WW2 era documents and discourse, reflecting both a bit of successful spin and the differing ‘weight’ of the Commonwealth Dominions as compared to Round 1.
Rather than Mr Murray’s little segue into creativity of the idiolect, a simpler, more historically accurate and, dare I suggest it, neutral term can be found in ‘British Commonwealth’ forces. Within that category, all chaps and chappesses who have done any reading in the area will understand that there are the Indian, British, Commonwealth (read Australian) and Empire/Colonial subcategories. Need an acronym for that? CW.
There have been other cases in Internet history of one chap’s terminology taking on an artificial veneer of accuracy simply through enough repetition, but that doesn’t make it authentic.
Gavins.