'overcautious' originates from English, specifically the prefix 'over-' (from Old English 'ofer') meaning 'above, beyond, too much' combined with the adjective 'cautious' (from Latin 'cautiosus' via Old French and Middle English).

'cautious' comes from Latin 'cautus' (past participle related to 'cav') and Latin 'cautiosus,' passed into Old French and Middle English as 'cautious'; the modern compound 'overcautious' was formed in English by prefixing 'over-' to 'cautious'.

The element 'cautious' originally carried the sense 'careful, wary'; with the prefix 'over-' the compound came to mean 'excessively cautious'—the modern sense emphasizing too much caution.