I like solving both American-style and cryptic crosswords now, but I never realized that the British called the black squares "dead squares" in English. In my e

I like solving both American-style and cryptic crosswords now, but I never realized that the British called the black squares "dead squares" in English. In my experience, this term is never used in American English, but it's the term most often used in Brazilian Portuguese crosswords (casas mortas). To my knowledge, it's also not used in Spanish (cuadros negros/celdas negras), French (cases noires), or Italian (caselle nere). I wonder how the dead-square terminology reached Brazil. I think the popularity of crosswords there was originally due to Italian immigrants, who might not have said "dead squares". I've heard people call the "letters [that] only take part in one word" unches (an abbreviation for "unchecked squares").