'stress-free' originates from the combination of 'stress' and 'free', where 'stress' refers to mental or emotional strain and 'free' means not subject to or affected by something.

'stress' comes from Middle English 'stresse', derived from Old French 'estresse', and 'free' comes from Old English 'frēo'.

Initially, 'stress' referred to physical pressure, but over time it evolved to include mental and emotional strain, leading to the modern usage of 'stress-free' as being without such strain.