'nonspastic' originates from the negative prefix 'non-' (from Latin 'non', meaning 'not') combined with the adjective 'spastic', which derives from Greek 'spastikos' (from 'spasmos', meaning 'a drawing or convulsion').

'spastic' changed from Greek 'spastikos' (σπαστικός) and entered scientific/medical vocabulary via Latin/Modern European usage, eventually forming the English adjective 'spastic'; 'nonspastic' is a modern formation by adding the productive negative prefix 'non-' to that adjective.

Initially 'spastikos' related to 'being drawn' or 'convulsive'; in modern medical English it came to describe increased muscle tone or involuntary stiffness ('spasticity'), and 'nonspastic' now denotes the absence of that condition.