What Does “X-Rated” Mean and Why Does Triple X Mean Super Sexually Explicit Material?

The first use of the X brand was on casks of English beer.

It indicated that the contents had been properly aged and had passed government approval after paying a ten-shilling duty, illustrated by the Roman numeral X.

Some brewers added extra Xs to suggest a more potent content, and smut peddlers followed suit.

When something is X-rated by the censors, its naughtiness is enhanced if more Xs are added.