From Arabic 'sifr' (zero), translating Sanskrit 'shunya' (void) — broadened from 'zero' to 'numeral' to 'secret code.'
A secret or disguised way of writing; a code; the arithmetical symbol 0 (zero); a person or thing of no importance.
From Old French 'cifre,' from Medieval Latin 'cifra,' from Arabic 'ṣifr' (zero, empty, nothing), a calque (loan-translation) of Sanskrit 'śūnya' (empty, void). The Arabic word 'ṣifr' named the concept of zero, which was transmitted from India to Europe through Arabic mathematicians. The semantic journey from 'zero' to 'code' occurred because early European users of Hindu-Arabic numerals
The word 'cipher' and the word 'zero' both derive from the same Arabic word 'ṣifr' (empty, nothing), which itself translates Sanskrit 'śūnya' (void). They entered European languages by different routes: 'cipher' came through Medieval Latin 'cifra,' while 'zero' came through Italian 'zefiro,' contracted to 'zero.' The two words are thus siblings separated at birth — both naming emptiness, one evolving