Zero and cipher are the same word, borrowed twice. Arabic ṣifr meant empty, itself a translation of the Sanskrit for the same idea, and it named the little circle that holds a place where there is nothing. Fibonacci wrote it into Latin in 1202 as zephirum, which wore down in Italian to zero. By another road it became cifra, and English got cipher, which first meant the zero, then any digit, and then, from the 1520s, a secret code, because the early codes swapped letters for numbers. In between, the money-changers of Florence were told in 1299 to keep the new figures out of their written accounts and use Roman numerals or words instead, by most accounts because a 0 is too easily turned into a 6 or a 9. So the sign for nothing came into Europe under suspicion, and the suspicion stuck to its name. To call a person a cipher is to say they count for nothing. To write in cipher is to hide something. It is the same word both times, and the same accusation: that an empty circle might be holding more than it shows.