'simply' originates from Latin, specifically the word 'simplus,' where 'sim-' meant 'one' and '-plus' meant 'fold.'

'simplus' transformed into the Old French word 'simplement,' and eventually became the modern English word 'simply' through Middle English.

Initially, it meant 'in a single way,' but over time it evolved into its current meanings of 'plainly' and 'merely.'