'annexitis' originates from New Latin/Neo-Latin, formed from Latin 'annexus' plus the Greek-derived medical suffix '-itis', where 'annexus' meant 'joined' or 'attached' and '-itis' meant 'inflammation'.

'annexitis' was formed in modern medical Latin from Latin 'annexus' (from 'ad-' + 'nexus', related to the verb 'nectere' meaning 'to bind') combined with the Greek suffix '-itis'; it later entered English medical usage unchanged as 'annexitis'.

Initially the components referred generally to a 'joined or attached part' and 'inflammation'; over time the term came to be used specifically for inflammation of the uterine adnexa (ovaries and fallopian tubes).