My old Dutch
An affectionate term for wife.
Unlike the many vaguely pejorative terms that the English have coined about their near neighbours, e.g. 'Dutch courage', 'Dutch treat', Dutch uncle' etc., 'my old Dutch' has nothing at all to do with the Netherlands. The expression is often cited as an example of Cockney rhyming slang. It is certainly a slang term that originated in London, but it isn't rhyming slang, as Dutch, being short for duchess, is an abbreviation rather than a rhyme. Some commentators have suggested that the expression is true CRS and that 'Dutch' is short for 'Duchess of Fife' and hence a rhyme for 'wife'. This assertion isn't supported by the facts. The term 'Dutch', meaning 'woman of showy appearance' was known by the early 18th century. Oliver Goldsmith referred to it in his comic play She Stoops to Conquer, 1773:
"This Stammer in my address... can never permit me to soar above the reach of... one of the Duchesses of Drury-Lane."
The name was used later as an affectionate term for wife or mother. J. F. Mitchell's ballad Jimmy Johnson's Holiday, 1882 is the earliest use of 'my old dutch' that I can find and seems to be a reference to someone of close acquaintance:
"Now he'd not a brown [a copper halfpenny],
nor a friend in town,
In fact he was quite undone;
He made a vow he'd never row with his old Dutch again."
The granting of titles to the British aristocracy is a subject that is minutely recorded and those records come in handy at this point. The Earl of Fife was created the First Duke of Fife on 27th July 1889, on his marriage to Princess Louise Dagmar, the daughter of the Prince and Princess of Wales. Until that date, there had been no title of Duchess of Fife. It is clear that the phrase came before the title and that 'Duchess of Fife' can't be the source of 'my old Dutch'.
The determination of some to establish that the term is Cockney rhyming slang has led to another inventive suggestion - that the term derives from 'Dutch plate', i.e. 'mate'. This is doubly unconvincing as 'Dutch plate' isn't a known 19th century expression and 'my old Dutch' means wife, not mate. It is likely that this supposed derivation has been confused with 'China plate', which is genuine CRS.
It was quite soon after Mitchell's publication that the song that made the phrase well-known was popularised by the music-hall entertainer, Albert Chevalier. Chevalier was a popular London-based variety artist of the late Victorian era and was widely known by the abbreviation 'AC'. That's something of a mercy, as his full name was Albert Onésime Britannicus Gwathveoyd Louis Chevalier. The lyrics of My Old Dutch were written by Chevalier in 1893, probably as a tribute to his wife Florrie although, if so, the 'been together now for forty years' line is something of a stretch of artistic license, as the couple didn't marry until October 1894.
We've been together now for forty years,
An' it don't seem a day too much,
There ain't a lady livin' in the land
As I'd swop for my dear old Dutch.
The supposed association of 'My old Dutch' with Cockney rhyming slang has been strengthened by the linking of the phrase with Chevalier, whose stage persona was very much the Cockney 'singing costermonger'. Amongst London costermongers, 'dutch' just meant 'duchess' - slang, yes, but rhyming, no.
The Duchess of Fife lived a quiet life out of the public gaze, but her position in society made her name well-known. 'Duchess of Fife' did become used as rhyming slang for wife, but that was in the 20th century, long after ''Dutch' and 'my old Dutch' were already well-established.