Was Lapine ever developed beyond the small glossary in Watership Down?

Question

One of the interesting features of Richard Adams's novel Watership Down is his invented language "Lapine" spoken by rabbits in the story. Mostly, of course, the rabbits are shown speaking in English, but we do get a fair few words of their vocabulary (hrair, thlay, yona, pfeffa, and so on) as well as a few hints at grammar or at least word construction (e.g. the usage of -rah and -roo as suffixes). Some editions of the book contain a vocabulary list at the back, although I think the edition I read as a child didn't have such a list printed in the book, being equipped instead with a handwritten list provided by a family member who'd read it before and left a sheet of paper inside the book.

Was this language ever developed beyond a short list of words and phrases? I know Adams wasn't an accomplished linguist like Tolkien, but he seems to have put some thought and effort into creating at least pieces of a fictional language which wasn't strictly necessary for the storytelling. I'm primarily asking about whether Adams himself designed more of the language than is shown in the novel, but would also be interested if there's any fan-made extension, a fuller Lapine language designed by others.

Answer 1

Yes, but not by Adams

_{... as far as I can tell, anyhow. Unless you count the sequel.}

As the Wikipedia page for the language says:

Linguists, academics, and fans of the original novel have further developed and refined the Lapine language since its 1972 creation.^[6][13] Authors, such as Patrick Jemmer (who corresponded briefly with Adams regarding Lapine), have made large-scale "recreations" of various possible historical stages of the language.

Spagirl has already found Jemmer, whose website contains further "development" of Lapine, as well as tracings of its "development" intermingling with other languages. He says:

My aim was to give free reign to my creativity, to enjoy the playfulness, and to investigate and demonstrate in as much detail as possible how a family of complex, interrelated, invented tongues develops, giving rise to syntax, a lexicon, scripts, and so on. My creative language play (a process I call “aleolinguistics”) is still going on.

See this PDF for further deets - Jemmer translated a poem into every stage of Lapine's "development".

Moving past Jemmer, quite a lot of links end up leading to Frithaes!, or an "Introduction to Colloquial Lapine". There's pretty detailed analysis of Lapine for a language-learning context: descriptions of tenses, word order, how to modify words, and an extensive Lapine-English dictionary containing lots of words I can't find references for in texts from Adams.

If we wish to stay closer to the original, I can point towards this dandy glossary where someone collected all words we have confirmation on meaning for (from the original book), as well as all words that can be extrapolated from the snippets of Lapine we are given.

And it seems remiss to not note that the sequel (third part of Tales from Watership Down) introduced a few new words as well. I've never read it, and can't seem to find a list of words which are known from it, but both Frithaes! and that glossary mention that it added words and I'll trust two random internet sources.

So yes, Lapine was developed beyond just the bits that Watership Down gives us.