biscuitsteamusic asked why “瑞” is pronounced with a r- initial in Mandarin but a s- in other Chinese varieties, using the transcription “瑞典” (Sweden) as an example.
The short answer would be an unexpected sound change. The theoretical initial in modern Mandarin should be sh- instead of r-.
The pronunciation of the character is given as “常去止合口三等” (Tangent: (d)zhwi, Polyhedron: zjyeh) and is a homophone of “睡” (Man: shuì, Canto: seoi6) in Middle Chinese. Following the devoicing to Modernized TCC, the modern Chinese result should be (t)shwi6~(t)shui6, which corresponds to the Mandarin “sh” or “ch” initial.
The exact reason for this unexpected change is unknown. It could have been an inconsistency in the sound change, a reversion to an old pronunciation that does not follow the evolutionary rules, etc. However, a point of interest here.
The Mandarin r- initial corresponds to the Modernized TCC j- /ʝ/ initial. This initial is pronounced somewhat like the English “zh” sound like the <s> in the word “pleasure”. In pre-modern Mandarin, the initial “r” was pronounced as /ʐ/, also pronounced like “zh”. Going off into serious linguistics a bit, the palatal consonants merged with retroflex consonants by Late Middle Chinese, hence there would be no distinction between them.
However, in Middle Chinese, a “zh” sound already existed, and that was devoiced in Modernized TCC to “sh”.
To illustrate, consider the following chain shift:
gn-, the original value of the Mandarin r-, became “zh” (j- in MTCC), while the original “zh” becomes “sh”. However, there is probably some inconsistency, with “瑞” being an exception, as it did not shift to “sh” like expected, instead keeping the “zh” sound, which later evolved into the modern r-.
This was perhaps a bit unnecessarily long but I hope it has been an interesting read.
