Idioms can be a real brain teaser. Like this one -  best thing since sliced bread*. This means that something is so good, a real favourite, a great invention. This is clear but – why sliced bread? Is it such a milestone in the history of humanity, that it is to determine an idiom?

Well, it seems so.

Sliced bread was first introduced in 1928. It is interesting to see how the invention was introduced to society. Chillicothe's Baking ad from the same year, for example, said sliced bread was “The greatest step forward in the baking industry since bread was wrapped.” The bread producers embraced the hype and so it began.

Nevertheless, in the beginning, the invention was not so popular but few minor improvements like the U-shaped pins which held the slices together made the product more appealing. And so it became a trend and the trend grew in necessity. It reached a point when during the World War II, when sliced bread was banned because of unnecessary use of resources, the housewives of the time made a real uproar. A woman wrote into the New York Times proclaiming “how important sliced bread is to the morale and sanity of a household.” The ban was lifted only after two months.
However, the first known record of the idiom is from 1952. The comedian Red Skelton said in an interview with the Salisbury Times: "Don't worry about television. It's the greatest thing since sliced bread".

*Sliced bread – an invention, surpassed by nearly everything since 1928.