The Spanish word 'testador' (meaning 'testator' or 'someone who makes a will') comes from the Latin word 'testari' meaning 'to testify' or 'to make a will'. The Latin word evolved into both the Spanish verb 'testar' (to make a will) and the Latin agent noun 'testator'. The modern Spanish word was formed by adding the agent suffix '-dor' to the verb 'testar', creating 'testador' - literally meaning 'one who makes a will'.

Some related and more common Spanish words include 'testar' (to make a will), 'testigo' (witness), and 'testimonio' (testimony). All these words share the Latin root 'testari' and relate to the concept of giving formal or legal evidence or statements. While 'testador' specifically refers to someone making a will, the related words expanded to cover broader contexts of testifying or bearing witness.

English speakers might recognize the connection to words like 'testament', 'testify', 'testimony', and 'testator'. These all come from the same Latin root 'testari'. Just as in Spanish, these English words all relate to formally stating or declaring something, whether in a legal context (like 'testator' - one who makes a will) or more generally (like 'testify' - to make a formal statement). The English word 'testator' is actually a direct cognate of Spanish 'testador', both meaning the same thing!