referred to as Pyarnu, an incorrect reverse-transliteration from the Russian Пярну. The town became part of independent Estonia in 1918 following World War...

is used for Estonian and Finnish ⟨ä⟩ – for instance, Pärnu is written ⟨Пярну⟩ in Russian, although the Russian pronunciation does not match the original...

Russian transliteration. Examples are the use of я ("ya") for ä (e.g. Pyarnu (Пярну) for Pärnu), ы ("y") for õ (e.g., Pylva (Пылва) for Põlva) and ю ("yu")...