'co-parent' originates from the prefix 'co-' meaning 'together' and the word 'parent', which comes from Latin 'parentem', meaning 'father or mother'.

'parentem' transformed into the Old French word 'parente', and eventually became the modern English word 'parent'. The prefix 'co-' was added to denote shared parenting responsibilities.

Initially, 'parent' meant 'father or mother', but with the addition of 'co-', it evolved to mean sharing parenting responsibilities.