Fleur / Phlegm
None of the Weasleys particularly cared for Bill's beautiful part-Veela fiancée, Fleur Delacour, but it took Ginny to come up with the contemptuous nickname 'Phlegm' to describe her.
The name 'Phlegm' is most obviously based on the similarity of sound between 'Fleur' and 'phlegm'. It is presumably also related to Fleur's use of throaty-sounding French 'r's when speaking English, which can be uncharitably compared to coughing up phlegm. The fact that phlegm refers to something particularly repulsive, namely the sticky mucus coughed up from the human respiratory tract, sets the seal on the sense of loathing that this nickname conveys.
As with all puns, the challenge for the translator is to come up with a nickname that is similar to 'Fleur' and conveys the disgusting properties of 'phlegm'.
The Mainland Chinese translator translates 'Phlegm' quite literally as 黏痰 niántán. This is incomprehensible to the Chinese reader, as it in no way resembles Fleur's name, which is 芙蓉 Fúróng 'Lotus' in the Mainland version. Accordingly, a footnote is added pointing out that Ginny calls Fleur 'Phlegm' (黏痰 niántán) because the sound is similar to 'Fleur' in English.
The translation of the word 'phlegm' here is of some interest. In English, 'phlegm' is the everyday word for what doctors know as 'sputum'. It tends to be associated with illnesses like colds, flu, bronchitis, and asthma. However, the Chinese term 痰 tán is broader in meaning than 'phlegm'. It is not necessarily a sign of illness and may refer to ordinary clear mucus that comes from clearing the throat. For instance, 吐痰 tù tán 'spit mucus' refers the habit of spitting (still fairly common in public places in China).
To make it clear that the 'phlegm' Ginny is referring to is not ordinary everyday mucus but the thick, sticky kind associated with illness, the translator uses the specific term 黏痰 niántán (literally, 'sticky/gooey phlegm').
As a translation of the pun, this effort must be regarded as merely Passable!
The Taiwanese translator comes up with a rather more ingenious solution.
Fleur in the Taiwanese version is known as 花兒 Huār meaning 'flower'. The normal Chinese word for flower is 花 huā, but one well-known characteristic of Beijing speech is the addition of a rhotic 'r' at the end of many words, thus 花兒 huār. Quite fortuituously, huār bears some similarity to the pronunciation of the French word 'Fleur', also meaning 'flower'. The name 花兒 Huār is thus quite an appropriate translation of 'Fleur'.
Since Fleur has a French accent, she habitually drops her 'h's, as in 'Arry'. In the Taiwanese translation, Ginny mocks this peculiarity by pronouncing Fleur's name not as 花兒 Huār but as 蛙兒 Wār, which means 'frog'.
The beauty of this translation is that it simultaneously captures Fleur's accent, gratuitously suggests that Fleur croaks like a frog, and also results in a word for something regarded as cold and slimy -- not phlegm but a frog. As a translation of the pun, this nickname must be regarded as nothing short of Brilliant!
The Japanese translator has Ginny call フラー Furā by the name ヌラー Nurā.
This does not make much sense until you look at the katakana letters used in writing Fleur's name. It is just a small change to transform フ fu into ヌ nu. Nurā is not actually a word, but sounds slimy in an onomatopoeic sense (compare ぬるぬるする nuru-nuru suru 'to be slippery, slimy, clammy, greasy). Nurā also echoes the names of Japanese movie monsters like モスラー Mosurā, the giant moth from Godzilla.
This rendition of the pun must also be regarded as Brilliant!
In the Vietnamese translation, Ginny calls Fleur Nhớt 'mucus, mucilage, slime'. For the Vietnamese reader, there is no apparent connection between Fleur and Nhớt, and the translator makes no attempt to explain how there might be one.
As a translation, this can only be rated a Fail!
Digression on Anti-Foreigner Sentiment
Ginny's use of the unfriendly nickname Phlegm to disparage a person from Continental Europe is one of several places where Rowling captures a particular attitude traditionally held towards Europeans.
Another example is Ollivander's rather dismissive comments about the wands of Continental participants in the Triwizard Contest at Book 4. Ollivander finds fault with the styling of Krum's wand (an oblique comment on stolid Teutonic qualities associated with Germans?) and dismisses Fleur's wand as possibly 'temperamental' because it contains a Veela hair. There is a detectable attitude that such Continental wands cannot compare with the solid, workmanlike British one.
Rowling describes these reactions without comment, which might lead one to suspect a sneaking sympathy for such sentiments. This would be very much at odds with her anti-discrimination message in other parts of the books, such as the anti-Muggle prejudice of some pureblood wizards. It is thus somewhat of a relief to find that the concept of respect for people regardless of their culture is spelled out quite clearly. In Book 4, intercultural friendships (verging on romance) form between Hermione and Krum and Hagrid and Mme Olympe.
More importantly, at the end of Book 6, 'Phlegm' proves that her devotion to Bill transcends temporary considerations of youth and beauty and she is fully accepted into the very British Weasley family.