Some idioms feel like they've been with us forever. We're used to saying it's 'raining cats and dogs', that we feel like 'a fish out of water' or that someone has been 'pulling our leg'. But other idioms have emerged relatively recently, such as 'Groundhog Day', 'first world problems' or 'computer says no'; we might hear people say that a long-running TV show has finally 'jumped the shark' or that a politician has deployed the 'dead cat strategy'. Just like new words, new idioms emerge in language all the time, and enter our vocabulary from TV, movies, sport, politics and the Internet. Michael Rosen talks to Gareth Carrol about the surprising origins of some of these modern idioms and why we pepper our speech with so much formulaic language. Dr Gareth Carrol is Senior Lecturer in Psycholinguistics at the University of Birmingham and is the author of 'Jumping Sharks and Dropping Mics: Modern Idioms and Where They Come From'. Produced by Mair Bosworth for BBC Audio