zetta-

First recorded in 1990–95; possibly an alteration of Greek zêta, which is the sixth letter of the final version of the Greek alphabet (representing Latin z). Greek zeta had the numerical value of seven: it replaced the original sixth letter of the Greek alphabet, wau, which was shaped like the Latin F and was pronounced like w, but the sound and the letter wau became obsolete in most Greek dialects during the 8th century b.c.