The letter C wasn't invented for English. It was invented several thousand years ago to write down the sounds of Phoenician, a language related to Hebrew and Arabic. At the time, the letter was called "gamel" or something like that, which means 'camel' (see the C?). It represented the G sound (the letter G was invented later, by the Romans).
Later on the Greeks started using the Phoenician alphabet and they used the letter to represent the G sound, too. Not having any camels, they called it "gamma"; the K sound was represented by the letter K, called "kappa". And later still, people in Italy used it, but they didn't have a G sound, so they used it for the K sound.
The Romans eventually wound up using this alphabet, with the letter C standing for the K sound, but they did have a G sound, so they put a little jot on the C and made it a G (they didn't use the letter K, except for words they borrowed from Greek)." (John Lawler)
"In the Norman French era, "C" was pronounced "S" before the letters "I,E,(Y)", and otherwise "K", After William the Conquerer captured England in 1066, English borrowed a lot of French words with French spellings, so "C" became a letter with two sounds. English also had words like "king, keep" where /k/ was pronounced before /e,i/, so the Greek letter "K" was reintroduced to keep things straight (more or less)." (Elizabeth J. Pyatt)
also
FINAL FANTASY ROCKS THE HIZZY!!