I believe the full answer would take a whole book. Here's the brief:
[tʰ]) is not alone here.
- The original Pali consonant list had consonants ordered according to where they are produced in human's vocal tract
(I believe this was a very unique feature of a writing system in the entire history of mankind);
- During the course of time, the phonetic value of the consonants have been changed; the entire groups of consonants 'folded' into voiceless aspirates;
- New symbols were introduced in order to restore the ancient pronunciation;
The table below shows Pali consonants and its original phonetic values. I compiled it from several sources.
One may notice second letters in cells, created to restore the ancient pronunciation after the original consonant changed its phonetic value. For instance, as soon as บ shifted
[b], the ป was introduced.
In some cases, it didn't work; see the sad story of ฟ, which was introduced after พ shifted
[pʰ], with the obvious aim to have some letter to write
[b], but then ฟ itself underwent another shift to
This table also shows how consonants obtained its consonant class (which governs tones):
- Voiceless unaspirated became Mid-class (green on diagram);
- Voiceless aspirated became High-class (red);
- All Voiced consonants became Low-class (blue);
I'm struggling to understand why the phonetic value changed if (as I believe) Thai did have the consonant /d/.
Richard Wordingham says in his article:
The second problem is the 'great consonant shift' whereby old voicing
contrasts were lost in much of East Asia, covering most Tai,
Mon-Khmer and Chinese dialects. (The change is not complete - some
areas have escaped the change.)
Consequently, the more conservative
Sinhalese and Burmese pronunciations are quite different to the Thai
and Lao (and Mon and Khmer) pronunciations. The Thai and Lao
pronunciations have replaced voiced stops by voiceless aspirates.
Is there any explanation for why the consonant ท was not simply given its original value?
Quoting the same article:
The ideas of the new symbols it to restore the ancient pronunciation.
Just as a Classical Latin pronunciation differs greatly from English
legal Latin or Roman Catholic Church Latin, and is very different to
how Latin loan words are pronounced in English, the modern Thai
consonant sounds are very different to the ancient Pali sounds.
[…] or perhaps some practice of pronouncing Sanskrit words transliterated using that consonant with /th/, while home-grown words used /d/?
Quoting the same article:
The problem with the traditional symbols is that they are pronounced
quite differently in Thai. พุทฺธ is
/buddʰa/ in the ancient
pronunciation, but พุทธ is
/pʰut-tʰa/ in Thai pronunciation. (Thai
doesn't use PHINTHU.) An analogy is that 'Caesar' is
/siːzə/ in British English, but is approximated as
in a Latin class in England.