'strain-variable' originates from the combination of 'strain,' which comes from the Latin word 'stringere,' meaning 'to bind tightly,' and 'variable,' from the Latin 'variabilis,' meaning 'changeable.'

'strain' evolved from the Old French word 'estreindre,' and 'variable' from the Old French 'variable,' eventually forming the modern English term 'strain-variable.'

Initially, 'strain' meant 'to bind tightly,' but over time it evolved to represent 'deformation or stress,' while 'variable' retained its meaning of 'changeable.'