'flapjack' originates from Middle English, specifically the word 'flap,' where 'flap' meant 'to flip or toss.'

'flap' combined with 'jack' in the 17th century to describe a flat cake or pancake, eventually becoming the modern English word 'flapjack.'

Initially, it meant 'a flat cake or pancake,' but over time it evolved to also mean 'a sweet oat bar' in the UK.