Also, it’s interesting that in the English-speaking world the conventional separator between "blocks" and "elements" is a double hyphen. From what I heard, originally in Yandex they used double underscores for that purpose, and a single underscore to separate a modifier from an element.
UPD: Actually, the original separators can still be seen on a Yandex page about BEM as a methodology: https://en.bem.info/methodology/css/
