The Spanish verb 'convencer' (to convince) comes from the Latin word 'convincere', which meant 'to convince' or 'to prove'. The Latin 'convincere' was formed by combining two elements: the prefix 'con-' meaning 'together' or 'completely', and the verb 'vincere' meaning 'to conquer' or 'defeat'. So etymologically, to convince someone literally meant to 'completely conquer' or 'thoroughly defeat' them in an argument or discussion.

Some related Spanish words include 'vencer' (to defeat, overcome), which comes directly from Latin 'vincere', and 'victoria' (victory), which is also related to the same Latin root. These words share the core meaning of conquering or defeating, though 'convencer' has evolved to specifically mean winning someone over through reasoning rather than physical conquest.

English speakers can easily remember 'convencer' by connecting it to the English word 'convince', which comes from the same Latin source 'convincere'. Other related English words include 'victory', 'victor', and 'invincible' (which cannot be defeated), all stemming from the Latin 'vincere'. The connection between convincing someone and achieving a kind of victory remains clear in both languages.