The Spanish word 'testifical' (meaning 'testimonial') comes from the Spanish verb 'testificar' ('to testify') combined with the adjective suffix '-al'. The verb 'testificar' itself derives from the Latin word 'testificare' meaning 'to bear witness', which was formed by combining two Latin words: 'testis' meaning 'witness' and 'facere' meaning 'to make or do'. So literally, the original Latin construction meant 'to make or act as a witness', which evolved into the modern Spanish adjective describing something related to testimony or witnessing.

Some related and more common Spanish words include 'testigo' (witness), 'testimonio' (testimony), and 'testar' (to make a will). All these words share the Latin root 'testis' and relate to the concept of witnessing or providing evidence. The verb 'testificar' is also more commonly used than the adjective 'testifical'.

English speakers can easily connect this word to several familiar English words like 'testify', 'testimony', 'test', and 'attest'. All these words share the same Latin ancestry through 'testis'. Interestingly, even the word 'test' (as in examination) comes from this root, as it originally referred to a vessel used to test metals, which served as a 'witness' to the metal's quality. The English suffix '-al' in words like 'testimonial' serves the same function as the Spanish '-al' in 'testifical'.