'bash' originates from English, specifically an English dialectal word 'bash', where its root is likely imitative and meant 'to strike' or 'a heavy blow'.

'bash' changed from earlier dialectal uses meaning 'a blow' or 'to strike' in the 17th–18th centuries and later developed additional senses; the slang noun sense 'party' emerged in mid-20th century American English and contributed to the modern uses of 'bash'.

Initially, it meant 'a heavy blow' or 'to strike'; over time it evolved to include figurative senses such as 'to criticize severely' and the informal sense 'a large party' (party meaning developed later).