From Proto-Indo-European, the t sound sometimes changed to th in Proto-Germanic, which in turn gave English the same th sound. However, I'm not sure when this change happened. I watched a video at https://www.youtube.com/watch?v=5ky7SjFRsFs and it showed a th sound. So, when did the sound change happen? (It seems to have happened before ~750 BCE because that is when Pre-Proto-Germanic was spoken.)

Extra: Could the sound change happen in the opposite direction? What I mean by this is the th sound changing to t again in part because of the sound and spelling. (It has already happened in some Germanic languages, and an example outside of Germanic is the th in greek changing to t in spanish)

  • around the time that p shifted to f, why do you ask? also, for all I know 750 BC was only 2000 years ago, exactly, and Germanic was invented by Wulfila to accommodate the Gothen king's lisp, because nobody dared confront him about and people grew weary of playing the embassadors new cloth around him. If I recall correctly. In other words: What's your evidence for a 750 BC unified PGmc as reconstructed?
    – vectory
    Jan 1, 2020 at 18:00
  • If you state that you know it has happened in the opposite direction (which it definitely has), why do you ask whether it can? It did, so it can...
    – LjL
    Jan 1, 2020 at 18:33
  • @LjL the way I understand that part of the question, it's not clear whether /*t/ in all descendents stems from a reversal, or was remaining unchanged throughout, or--since we are not entirely sure about the phonetic value of PIE *t, whether its IPA("th") that is the constant, though typologically unlikely.
    – vectory
    Jan 1, 2020 at 21:06
  • Related part of the Wikipedia talk page: en.wikipedia.org/wiki/… Jan 2, 2020 at 11:36

2 Answers 2


The sound law that explains how /t/ turned into /θ/ is called Grimm's law; I would recommend reading up on it in literature on on Wikipedia. The subsequent law that explains how /ð/ appeared is called Verner's law, which I would recommend looking up after Grimm's law since it operates on the results of that.

Faroese is the modern Germanic language that I would say most cleanly has turned /θ/ into /t/ again. Late Old Swedish, 15th-16th century specifically, also turned word-initial /θ/ into /t/, but that happened after a previous sound change that also changed /θ/ into /ð/ in short words (almost identially to how "them", "thou" and "then" start with /ð/ in English), and since /ð/ turned into /d/, and was written as such, the results are less obvious in Swedish. The same would probably hold for Danish, but I know less about medieval Danish and how it lost its dental fricatives.

  • calling somebody to "reading up on" is not an answer, and rather impolite.
    – vectory
    Jan 1, 2020 at 18:05
  • Faroese also has a double reflex of word-initial /θ/: it is /h/ in function words, /t/ elsewhere Jan 1, 2020 at 21:19
  • 3
    @vectory: The OP has clearly not identified Grimm's Law or done any further research (they "watched a video"). Obviously they need to do some, because there's tons of stuff on the web about it. Under those circumstances, I think being told to read up on something is quite appropriate and certainly not rude.
    – jlawler
    Jan 2, 2020 at 2:04

The change t > fricative th must be dealt with the whole picture of PIE voiceless stops becoming fricatives in Proto-Germanic. That is to say: p t k > f th h. Indeed, this is the first mutation of Germanic.
As far as dating is concerned, it's hard to be precise. We can see that:
1. Germanic languages had already acquired their specific look, when they began to be written,
2. When Germanic languages got in contact with Latin, new words like *kat "cat" and *kasi "cheese" did not undergo the change. So the change is older than the Roman Empire.
3. There are also Celtic-Germanic contact words like *bukk- = buck, I suppose some people have studied them.
All this suggests the change must be significantly older than the Common Era, possibly even going into the second millennium BCE.
Besides, the first mutation of Germanic is in fact two changes: consonants changed and stress changed. These changes are major rearrangements of the language. This must have taken a quite long period of time.

  • As for cheese, consider Hütten-Käse, (literally cottage cheese, but fits *k > *h; cp ferment vs Fr fermer "to close, shut")
    – vectory
    Jan 2, 2020 at 17:30
  • Whereas *k can as well come from *gw- (compare "to come"), also in Armenien btw. That's *b in Hellenic, hence cow ~ bous, bovine. This also explains cum, perhaps, cp Ger Kuppenkäse "dick cheese", haha. I was actually hoping to find kwas, the fermented milk yoghurt drink, but have no idea where that came from and I won't search now. The romance word for cheese is chiefly fromag-, not casa "house", so why would we not borrow that? Questions over questions.
    – vectory
    Jan 2, 2020 at 17:51
  • *kasi "cheese" is obviously from Latin case(um), not casa.
    – user23769
    Jan 2, 2020 at 19:42
  • I don't know what's obvious about it. Loans from Latin into Germanic proper are rarely admitted and without known historic pathway.
    – vectory
    Jan 2, 2020 at 23:13
  • The wordplay with casa was no mistake. Incidently, when I looked up leather for its development of Th, I found: Armenian translation կաշի (kaši), supposedly with a relation to Semitic. That can't possibly have anything to do with cheese. Let's see Latin aluta "leather", assigned a root akin to aluminum; AGr bursa; modern Greek derma (again cp ferm-, if by stretch of the imagination *d- ~ *dh- can be explained). leather and cheese were trade items and it stands to reason that "cover, skin" fits what I implied before.
    – vectory
    Jan 2, 2020 at 23:17

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