An idiom, according to dictionary.com, is “an expression whose meaning is not predictable from the usual meanings of its constituent elements”.
My favorite idiom is “jumping the shark”. It is used to describe a story, product, or company that introduces something new that clashes with or is an extreme exaggeration of its original concept.
I love finding out the sources of these phrases!
This idiom was coined by radio personality Jon Hein in response to an episode in the fifth season of the American television sitcom “Happy Days”, in which the character Fonzie performs a water-skiing stunt of jumping over a live shark. The show was set in the 1950’s with the central characters being a Midwestern middle class family who rented an over-garage apartment to a motorcycle-riding, leather-jacket-wearing, very “cool” character named Arthur Fonzarelli, or “Fonzie”. He was certainly a daredevil, but water-skiing was not within his scope of skills. But Fonzie could never back down when somebody challenged is “cool”-ness or his bravery.

While this idiom is most frequently used in references to stories (televisions, movie sequels, books), it has also come to be used in references to companies and products that have “jumped the shark” with the introduction of new products and features that are discordant with their core intent.
Please share in the comments an example of something that you think “jumped the shark” and why. Or share your favorite idiom and its source.
Let’s make this a great Monday!
Source: Wikipedia - Jumping the shark