Did you know that 'flavour of the month' originated in a marketing campaign in American ice-cream parlours in the 1940s, when a particular flavour would be specially promoted for a month at a time? And did you know that 'off the cuff' refers to the rather messy practice of writing impromptu notes on one's shirt cuff before speaking in public?
These and many more idioms are explained and put into context in the Oxford Dictionary of English Idioms
