'approbation' originates from Latin, specifically the word 'approbatio', where 'ad-' meant 'to' and 'probare' meant 'to test, to approve'.

'approbatio' passed into Old French and Middle English (e.g. Middle English 'approbacioun'), eventually becoming the modern English word 'approbation'.

Initially, it referred to the act of proving or approving ('the act of testing/confirming'); over time it shifted to the current sense of 'approval' or 'praise'.