'unitless' originates from the English word 'unit' combined with the suffix '-less', where 'unit' meant 'a single thing or person' and '-less' meant 'without'.

'unit' changed from the Old French word 'unité' and eventually became the modern English word 'unit'.

Initially, 'unit' meant 'a single thing or person', but over time it evolved into its current meaning of 'a standard measure'.