The Spanish verb 'probar' (meaning 'to test' or 'to prove') comes from the Latin verb 'probare' with the same meaning. 'Probare' itself was derived from the Latin adjective 'probus' meaning 'good' or 'honest'. The word 'probus' was formed by combining two Latin elements: the prefix 'pro-' meaning 'forward' or 'in front' and the suffix '-bus' indicating tendency. The semantic development from 'good/honest' to 'test/prove' suggests that something proven or tested was considered trustworthy and good.

Several common Spanish words share this Latin root, including: 'prueba' (test, proof), 'probable' (probable, likely), and 'aprobar' (to approve). All these words carry the core concept of testing, verifying, or demonstrating something to be true or good.

English speakers might recognize the connection to words like 'prove', 'proof', 'probable', and 'approve', which all come from the same Latin root 'probare'. Just as in Spanish, these English words all relate to testing, demonstrating, or verifying something to be true. The word 'probe' is also related, maintaining the sense of testing or examining something thoroughly.