Why does English still have the “TH” sound?
The interesting thing about this topic is that English is one of two languages of the Germanic family that has retained the feature commonly called the <TH>-sound which stands for the dental fricatives /θ ð/. If you have a look at the map below which highlights the Germanic tongues in red, only Icelandic and British English (from England, Wales, Scotland + Northern Ireland) in darker red sport these sounds. It is also fascinating because there was a time when the ancestors of all these tongues had dental fricatives but lost them over the last centuries.
Then, why did English maintain a sound that was lost in almost all its sister-languages despite centuries of evolution side-by-side?
First, you have to understand that on the whole, Germanic languages phonetically stand out from the rest of the Indo-European languages for a set of processes that made original IE sounds move one step closer towards fricatives. These evolutions were named Grimm’s Law, after Jacob Grimm discovered this phenomenon in 1875. This is a brief summary of what happened during the splitting of Germanic away from common IE:
This translates into these instances:
- Greek: Podos/ Latin: Pedis/ Sanskrit: Pada vs English: Foot/ Danish: Fod/ Gothic:Fotus.
- Greek: Tritos/ Welsh: Trydydd/ Russian: Tretij vs English: Third/ Old Saxon: Thriddio/ Icelandic: Þriðji.
There are many more examples but the most relevant here is of course the change of alveolar/dental stops /t d/ into the dental fricatives /θ ð/. This is the first steps in explaining the presence of dental fricatives in English. They descend from a millennia-old process that saw these sounds develop in all Germanic languages.
When Grimm’s Law was accepted, a new problem arose; some words clearly didn’t fit within the frame hypothesised by Grimm. For example, Proto-Indo-European pa’tēr turned into father instead of the expected fader while PIE ‘brahtēr gave brother like Grimm’s Law predicted. The alternation can also be found in different forms of verbs. So of course, Grimm must have missed something. It turned out that the solution lies in the change of accents in Proto-Germanic. While stress was relatively free (meaning rather unpredictable) in PIE, PG stress shifted and was placed on the root of the word. The evolution of the phonemes did not affect the consonant if it was word-initial or right behind a stressed vowel. The evolution of these consonants are illustrated in the table below:
This is the reason why PIE /t/ became [θ] and then [ð] in PG for *fadēr while *brōþēr remained untouched. This event helped increase the number of instances of dental fricatives in Proto-Germanic. But it still doesn’t account for English dental fricatives. Be patient.
High German Consonant Shift
A new phenomenon took place in the southern dialects of German in the 5th century that consisted in a large-scale shift in the consonantal system. By the mid-5th century, Old English had already been brought to Britain and thus remained utterly unaffected by these changes whose relevant features are the following:
- θ > d
- β > b
- ð > d
- ɣ > g
As you can see, the dental fricatives evolved into stops and were consequently lost in the phonology. The HGCS was not restricted to German as certain elements can be found as well in Dutch, Low German and Scandinavian Germanic. Probably under the influence of German in the following centuries, Danish, Norwegian and Swedish lost their own dental fricatives as there were multiple and intense cultural and linguistic exchanges between German and “Scandinavian”.
While English, isolated geographically from the rest of Europe and from Germanic influence because of Roman and Norman Conquest, kept /θ ð/. It’s interesting to note that Britons did not have as much as Romans and Normans the inclination to write. Manuscripts by monks may have helped bring a certain standardisation to the language.
Two additional and contradictory phenomena took place in Middle English where /d/ changed to [ð] and /ð/ to [d]. This is why fader changed to father and murðer changed to murder. The sequence of /d/ + unstressed ending -er triggered its evolution to [ð].
In short, dental fricatives appeared in Proto-Germanic via Grimm’s Law and Verner’s Law and Old English managed to maintain [θ] and [ð] because it left the continent before the effects of the High German Consonant Shift could be felt. Its geographical isolation (being on an island) certainly helped protect the relic of the Germanic legacy.
I saw once that Welsh may have had an influence on the upholding of these sounds since both languages had them. However, Latin and French were much more powerful influences on English but that did not impact the keeping of the dental fricatives so a foreign language influence is not really believable. However, French might have contributed to the phonemisation of [ð]. Before French came to Britain, /z v ð/ were only the voiced allophones of /s f θ/. By introducing new graphemes for sounds that were not “official” in English, it turned them into unquestionable elements of the phonology of English.
Isolation may be the biggest driving force on the upholding of these sounds since Icelandic, in a relative similar position, is the only other Germanic language with dental fricatives.