'henceforth' originates from Middle English, specifically the combination of 'hence' and 'forth', where 'hence' meant 'from here' and 'forth' meant 'forward'.

'henceforth' changed from the Middle English word 'hennes-forth' and eventually became the modern English word 'henceforth'.

Initially, it meant 'from this point forward', and this meaning has largely remained the same in modern usage.