Where does “хатуугийн тэмдэг” come from?

хатуугийн тэмдэг (Mongolian) comes from Russian твёрдый знак — Name of the letter Ъ, ъ, the hard sign.

Ancestry of “хатуугийн тэмдэг”, step by step

хатуугийн тэмдэг traces back through two separate lines of ancestry.

via Russian твёрдый знак

StepLanguageWordMeaning
1Russianтвёрдый знакName of the letter Ъ, ъ, the hard sign

via Mongolian тэмдэг

StepLanguageWordMeaning
1Mongolianтэмдэгsign; mark; symbol
Every word from Russian твёрдый знак