There is quite an amount of so-called diachronic constructed languages, taking one language (historical like vulgar Latin, or modern like present-day English) and applying some sound shifts and grammatical shifts to this language.

Going the other way round, constructing a language that is older in time than the given language and is meant to be a plausible antecessor of that language is much rarer. I am aware of Arcaicam Esperantom as an example of such a language, but I'd like to learn of more of them.

So what are examples of reverse diachronic constructed languages?

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    Would Proto Indo-European and other similar projects count for what you are looking for? Oct 2, 2021 at 13:18
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    No, I want to exclude scientific reconstructions of Proto-Languages and concentrate on the artistic side of diachronics.
    – Sir Cornflakes
    Oct 3, 2021 at 19:14
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    I believe Tolkien worked both forward and backward in making the Elvish languages. Oct 4, 2021 at 2:42
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    worth noting that, because sound changes are not generally reversible, this is much harder, and requires much more fine-grained work (e.g. at the word, or at least root level, rather than at the scale of an entire lexicon) than working forwards in time (it's partly for this reason that many people recommend starting from a proto-lang if there's any chance you may want a sister language at some point in the future, the other reason being that it aids in producing naturalism)
    – Tristan
    Oct 4, 2021 at 15:24

1 Answer 1


Possibly the most well-known example is Mark Rosenfelder’s Proto-Eastern, which was developed to be a plausible ancestor of Verdurian. Probably there are others as well.

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