J is the tenth letter of the alphabet, but it was the last letter to be added to the alphabet.
The Egyptians started with the hieroglyph of a hand. Two letters, I and J, developed from this hand symbol. The Semites turned the symbol upright, and then the Phoenicians just drew a straight line. The Greeks named their letter iota. The Latins just used the letter I. In Medieval times, sometimes scribes put a curl on the bottom of the letter I when it was used in certain positions, and this developed into the modern J.