'smoothly-moving' originates from the combination of 'smoothly' and 'moving', where 'smoothly' is derived from 'smooth' meaning 'even or without roughness', and 'moving' from 'move' meaning 'to change position'.

'smooth' changed from Old English 'smōð' meaning 'free from roughness', and 'move' from Latin 'movēre' meaning 'to change position'.

Initially, 'smooth' meant 'even or without roughness', and 'move' meant 'to change position'. The combination 'smoothly-moving' retains these meanings in a descriptive form.