Growing up in Singapore as a child from the Teochew (Cháozhōu 潮州, S.E.China) dialect group, I’d hear derogatory / pejorative remarks made about other dialect groups. The Cantonese (S.E.China) put too much oil and salt in their cooking. The Hokkiens (from Fújiàn 福建 Province, S.E.China) are uncouth — they apparently have the biggest range and the most vulgar of swear words and phrases, so vulgar I didn’t dare listen, never mind repeat. The Hainanese (from Hainan Island, S.E.China) were called “white stomachs”, which is a kind of sea fish: it has a white underbelly and floats in the water upside down, white underbelly facing up, thus making it very easy for fishermen to spot and catch them, hence stupid. Similarly, there were jokes / comments about the Malays and the Indians.
When I went to work in Taipei, I heard similarly critical comments about three regions (there must be others): people from Anhui Province (further north of S.E.Chia, inland westwards from Shanghai) are fierce; people from Sichuan Province (S.W.China) and Hunan Province (central China) are fiery (because of the hot food they consume) and can outdo anyone in a row.
Coming to London, I came across jokes about (and labels for) the Irish and the Scots, sometimes about northern English people.
When I started going out with a Swiss man, I heard that the Swiss have jokes about the Austrians, and the French have jokes about the Belgians.
It then dawned on me that it’s geographical proximity (and therefore familiarity) that decides who the targets of disparagement would be.
The Chinese community in Singapore in the 1960s consisted mainly of Hokkiens (the biggest group at the time), the Cantonese, the Teochews, the Hainanese and the Hakkas. It’s not a coincidence, I think, that they’re all from S.E.China. There were no derogatory remarks about people from Anhui, Sichuan or Hunan, because we didn’t have them in Singapore at the time.
Ditto the English jokes/comments about the Irish and the Scots. Ditto the Swiss and French ones. They’re all neighbours, or close enough. I have a feeling there’ll be Scandinavian ones about each other.
I call this “sibling rivalry”.
It can also be applied to people from the same sex: in my experience, women tend to be more competitive with (and often, catty about) other women, and men with men, rather than across the sexual divide.
An example from my personal experience: when I started my relationship with the Swiss man, I told a good friend, Bernhard, about it, adding, “And he’s a German speaker, too!” Bernhard, who’s German, said, “That’s what he thinks.”
Update 271117: An ex-student’s father, who’s from Tianjin, China, said last night when I told him the Hainanese story: "People in mainland China think people from Hainan are very clever." Proves my Sibling Rivalry theory, I think — Tianjin in north China is much further from Hainan Island in the south-east.