The word came to Europe with Arabic numerals. From "zero," it came to mean "any numeral" (early 15c.), then (first in French and Italian) "secret way of writing; coded message" (a sense first attested in English 1520s), because early codes often substituted numbers for letters.
来自古法语cifre,零，来自意大利语cifra,零，来自阿拉伯语sifr,零，来自s-f-r,空的，空无，词源同zero.因为古人早期对数字零的认识不足，该词逐渐被赋予神秘色彩，词义也由零引申为密码。