'approvable' originates from Latin, specifically the word 'approbare', where 'ad-' meant 'to/toward' and 'probare' meant 'to test, prove or approve'. The adjective 'approvable' is formed in English by adding the suffix '-able' to 'approve'.

'approvable' developed from Middle English 'approven/approve' (borrowed via Anglo-French/Old French from Latin 'approbare'), with the productive English suffix '-able' attached in Early Modern to Modern English to yield 'approvable'.

Initially the Latin root 'probare' had the sense 'to test, prove', which in Late Latin and Old French shifted toward the sense 'to approve, assent'; in Modern English 'approvable' specifically means 'capable of being approved' or 'deserving approval'.