Cryptography is the science (and art) of writing messages that no one but the intended receiver can read. The name derives from either the French word cryptographie or from Modern Latin cryptographia both of which find their roots in the Greek kryptos “hidden” + graphia “writing or recording”.
Historically, the human race needed to communicate and share information with others, but it also needed to communicate selectively. That's why this “art” started to be performed, hiding messages from unauthorized people until the message reaches the intended hand. The first evidence of cryptography is the use of hieroglyphs by the Egyptians.
Later on the Romans popularized the cryptography method known as the Caesar Shift Cipher which relies on shifting the letters of a message by an agreed number. Then, the receiver of the message would shift the letters by the same number again to obtain the original message.