'varmistaa' originates from Finnish, specifically from the adjective 'varma' plus the verb-forming suffix '-istaa/-staa', where 'varma' meant 'sure, certain'.

'varma' comes from Proto-Finnic *varma (from an older Uralic root), and the verb 'varmistaa' developed in Finnish by adding the causative/verb-forming suffix to form 'to make certain'.

Initially related to the adjective meaning 'sure' (i.e. making something sure); over time it evolved into the active verb meaning 'to ensure' or 'to confirm'.