'dimensionless' originates from the word 'dimension' combined with the suffix '-less', where 'dimension' comes from Latin 'dimensio', meaning 'a measuring'.

'dimension' transformed from the Latin word 'dimensio' and eventually became the modern English word 'dimension'.

Initially, 'dimension' meant 'a measuring', but over time it evolved to refer to measurable extents in space, and 'dimensionless' came to mean lacking such extents.