I noticed that at the beginning of Great Expectations by Charles Dickens that Mr. or Uncle Pumblechook kept calling Mrs. Joe mum. Why is that? I know for sure that Mrs. Joe didn't give birth to him, but I still am confused. Is it because of Victorian lifestyle manners?
“Mum” is a dialect spelling of “ma’am”, a shortened form of “madam” that was “formerly the ordinary respectful form of address to a woman” (OED). Here are a couple of examples, in both cases a servant addressing a woman of higher social status:
… for not to be immediately forthcoming when called for, was regarded as a grave and inexcusable offence: not only by my pupils and their mother, but by the very servant, who came in breathless haste to call me, exclaiming, “You’re to go to the schoolroom directly, mum—the young ladies is WAITING!!”
Anne Brontë (1847). Agnes Grey, p. 183. London: Thomas Newby.
At last the gentleman did come, and was shown up with all the ceremony of which Mrs. Bunce was capable. “Here he be, mum.”
Anthony Trollope (1866). The Belton Estate, volume III, p. 159. London: Chapman and Hall.
(Note in both cases the use of non-standard grammar in the servant’s speech: “ladies is” in Brontë and “he be” in Trollope.)
Dickens uses dialect spelling to distinguish his characters and place them as to social position and accent. In Our Mutual Friend, the “ma’am” of the footman Rokesmith is contrasted with the “mum” of the foundling Sloppy:
The four members of Council looked at one another, and paused. ‘Shall he be brought here, ma’am?’ asked Rokesmith.
‘Yes,’ said Mrs Boffin. Whereupon the footman disappeared, reappeared presenting Sloppy, and retired much disgusted. […]
‘And how is Betty, my good fellow?’ Mrs Boffin asked him.
‘Thankee, mum,’ said Sloppy, ‘she do pretty nicely, and sending her dooty and many thanks for the tea and all faviours and wishing to know the family’s healths.’
Charles Dickens (1864). Our Mutual Friend, volume II, p. 187. New York : J. Bradburn.
In Barnaby Rudge, the housemaid Miggs is represented as pronouncing “ma’am” as “mim”:
“Master’s come home, mim,” cried Miggs, running before him into the parlour. “You was wrong, mim, and I was right. I thought he wouldn’t keep us up so late, two nights running, mim. Master’s always considerate so far. I’m so glad, mim, on your account. I’m a little”—here Miggs simpered—“a little sleepy myself; I’ll own it now, mim, though I said I wasn’t when you asked me. It an’t of no consequence, mim, of course.”
Charles Dickens (1841). Barnaby Rudge, p. 38. Philadelphia. T. B. Peterson.