Right now, the word cipher is used to denote encrypted messages, but five hundred years ago, it meant "zero". This is because it came to be associated with numerals in general, then with codes using numerals, and finally with the modern definition. It comes from Old French cifre, Latin cifra, and ultimately Arabic sifr, which still meant "zero". Since the Roman number system did not have any concept of nothingness, sifr also gave us the word for "zero" in many European languages, including French chiffre, German ziffer, and English zero; the term likely comes from an earlier Arabic word, safara, which meant "to be empty". That in itself has an interesting etymology; it's named after the Arabic month of Safar, the second of the Muslim calendar, because that time was known for pagan looting that would leave all the houses empty.
Adam Aleksic, a rising sophomore studying linguistics and government at Harvard University, has been described as the internet's sixth most famous etymologist. He also has disturbing interests in politics, vexillology, geography, board games, conlanging, and law.