XXX, Roman and otherwise...

"X-rated" originated in 1968 by the Motion Picture Association of America as a guide for moviegoers. At the time, this designation excluded anyone under 17 from viewing the film. Additionally, in the Middle Ages illiterate individuals signed their names with the X as a sign of faith since it was a direct representation of St. Andrew's Cross.

Farther back in the recesses of history we find that XX was slang for the 20 dollar bill in the 19th century originating around 1850. XX meaning "20" in Roman numerals.

XXX, on the other hand, derives from 19th century alcohol content labeling. X, XX, and XXX were used to indicate the level of alcohol, much like proof is used today. Of course, the triple chi has also been used to designate kisses since, according to some, the intersection imitates two mouths in contact. An uncorroborated story reported by Ronald Seigal of SUNY at Stony Brook indicates that the XXX was also used at the end of transmissions by telegraphers to note the end of transmission since the combination could not be found in any English word.