The name is a description: po Labe, along the Elbe. The Polabian Slavs occupied much of what is now northeastern Germany — Mecklenburg-Vorpommern, the central Mittelmark of Brandenburg, eastern Saxony-Anhalt, the eastern parts of Wendland in Lower Saxony, and into Schleswig-Holstein, Ostholstein and Lauenburg. Polabian was still being spoken in and around Lübeck and Oldenburg into the sixteenth century. The poorly attested Slavic dialects of Rügen appear to have had more in common with it than with the Pomeranian varieties further east. In the south it ran up against the Sorbian language area of Lusatia, which is still spoken today. Polabian belonged to the Lechitic branch, which makes it a close relative of Pomeranian and Kashubian and a cousin of Polish. Century by century the language area contracted under German settlement, until by the middle of the eighteenth century what remained was a pocket in the Wendland, and Low German had taken over there too.

Polabian held onto features that most of the Slavic family had let go. It kept the nasal vowels, so Proto-Slavic *pętь came through as pąt. It kept the aorist and the imperfect. It kept traces of the dual number, the grammatical form for exactly two of something. And it never underwent one of the sound changes that reshaped the rest of the family, so words that metathesised elsewhere stayed put here. At the same time it went its own way with enthusiasm. Closed vowels broke into diphthongs; o shifted toward ö and ü, a toward o; g and k softened in some positions into d' and t'. Proto-Slavic *dьnь became dan, day. *vъšь became vås, louse. *tьma became tåmă, darkness. The bones are recognisably Lechitic. The surface is not.

The pressure of the surrounding language shows up everywhere, and not only in vocabulary, though Polabian absorbed a great many Middle Low German words. It built a future tense with cą, I want, plus the infinitive — ci sneg ai̯t, it will snow. It developed a second perfect tense on the German pattern, with have or be plus a participle: vån mo nodenă, he found. It formed the passive with vardot, taken straight from German werden. The old Slavic word for a hundred was lost and replaced by disą(t)diśǫt, ten tens, or by a construction built on stíďə, borrowed from Middle German stige, a score. A language dying under another language does not simply fall silent. For generations it goes on working, borrowing the machinery of its replacement to keep saying what its speakers need to say.

Almost everything known about Polabian was collected in the last decades, by people who could see what was coming. The most important record is the Vocabularium Venedicum, compiled between 1679 and 1719 by Christian Hennig von Jessen, a Lutheran pastor at Wustrow, who worked with a Polabian-speaking farmer named Johann Janieschge from the village of Klennow. Others assembled phrase lists and word lists and gathered folklore. Only one of the collectors was himself a native speaker: Johann Parum Schultze, a farmer, whose manuscript runs to 310 pages of which just thirteen are of use to linguists. The rest is the village chronicle he was actually setting out to write. It is worth pausing on that ratio. A man recording his own dying language gave it thirteen pages, because he had a farm and a village and a life, and the language was simply the thing he thought in.

The language survives most durably on the map. Wustrow, where Hennig von Jessen kept his notebook, is Polabian Våstrüv and means simply island. Lüchow is Ljauchüw. Sagard, Gartow and Krakow carry Slavic roots too. And Berlin most likely does as well, from a Polabian stem berl- or birl- meaning swamp — the capital of Germany named, in all probability, in a language that has had no fluent speakers for two and a half centuries. That is not quite the end of it. Small, unorganised groups have started learning Polabian from the surviving materials, and as of 2023 there were a few limited speakers again, with more resources available to work from than at any point since Hennig von Jessen closed his book. Emerentz Schultze's language is not coming back as anyone's mother tongue. It is, at least, being read aloud again.