'nonannexation' is formed in modern English by adding the prefix 'non-' (meaning 'not') to 'annexation.' 'Annexation' itself comes from Old French 'annexation' and Medieval Latin 'annexatio', ultimately from Latin elements meaning 'to tie' or 'to join.'

'non-' + 'annexation' combined in modern English usage to create 'nonannexation' (literal: 'not annexation'). 'Annexation' entered English via Old French 'annexacion' / Medieval Latin 'annexatio' from Latin roots.

Originally, the Latin root carried the sense 'to tie to' or 'to attach.' Over time this developed into the legal/political sense of 'adding territory' or 'incorporating' a place; 'nonannexation' therefore came to mean 'the refusal or absence of that addition.'