'nonlinearity' originates from the prefix 'non-' meaning 'not' and the word 'linearity', which comes from 'linear', derived from Latin 'linearis', meaning 'of or pertaining to a line'.

'Linearity' transformed from the Latin word 'linearis' and eventually became the modern English word 'linear', with 'nonlinearity' forming as a negation.

Initially, 'linear' meant 'pertaining to a line', and 'nonlinearity' evolved to describe systems or equations that do not follow a straight line or proportional relationship.