The palatalization of Proto-Turkic /č/ to /č́/ and then the weakening of the affricate’s initial stop to give /š́/ or /š/, is a notable areal feature extending from the Volga–Kama region into Kazakhstan. In the second volume of Róna-Tas and Berta’s Western Old Turkic (Harrassowitz, 2011), which reconstructs the ancestor of Volga Bulgarian and Chuvash on the basis of loanwords into Hungarian, the authors mention how the Tatars, whose own language would soon undergo the same evolution, were confronted by this change already almost complete in Volga Bulgarian:
Important is the bilingual inscription of Tatar Šapkino. In the Arabic inscription containing Volga Bulgarian words, the name of the deceased lady is written as J̌eker, and should be read as /č́eker/, while on the other side of the same stone, the same name is written as Šeker. What was perceived as /č/ by the Volga Bulgars was heard by the Kipchak Tatars as /š/.
Tatarskoe Shapkino is a village in south-central Tatarstan. A description of the Arabic portion of this inscription can be found in Khakimzjanov’s Язык эпитафий волжских булгар (Moscow: Nauka, 1978) on pages 158–159:
هو الحى الذى لا يموت
هذه روضة مستورة
المطهرة الصَّالحة الصائـنة الطيفة
شكر الجى بنت عثمان البلفارؾ
الهم ارحمها رحمة واسعة توفيت
الى رحمة الله تعالى فى اليوم الرابع و العشريں
Huwa-l-xäjji-l-läzi lä jämutu wä küllü häjjin säjämutu. Haẕihi rawḍatu-l-mästüräti-l-muṭahhiräti-ṣ-ṣalixäti-ṣ-ṣa’inäti-ṭ-tajfäti Šäkär-älči bint Gos̱man äl-Bolɣari. Äl-lähummä ärxämha räxmätän wäsigätän. Tuwufijjat ilä-r-räxmäti-l-lahi tägali fi-l-jawmi-r-rabigi wä-l-gišrinä
He lives who does not die, but every living thing dies. This is the plot of the chaste, devout, pious, caring, compassionate Šeker-elči, daughter of Osman the Bulgarian. God, have mercy on her with your great mercy. She was entrusted to the mercy of God the Most-High on the twenty-fourth day.
The monument lies in the village cemetery and has dimensions of 160×60×23 cm. It has been inscribed in two languages: on the obverse there is an Arabic-language inscription written in relief in the Thuluth style of calligraphy, while on the reverse a Turkic text has been inscribed in the Bulgarian variant of the Kufic style. There is also relief writing on the sides of the monument.
A piece of pottery is lying nearby with writing on both sides (but it has not been successfully deciphered). This may give the date of the inscription in question.