The Spanish adverb 'vehementemente' (meaning 'vehemently') comes from combining the adjective 'vehemente' with the adverbial suffix '-mente' (equivalent to English '-ly'). The adjective 'vehemente' traces back to the Latin word 'vehemens', meaning 'impetuous' or 'violent'. The Latin term itself is a compound of two elements: 've-' meaning 'away from' and 'mens' meaning 'mind'. So etymologically, something vehement was considered to be 'away from the mind' or 'mindless' - suggesting intense, uncontrolled emotion or action.

A simpler related Spanish word is 'vehemente' (vehement, passionate), which is the adjective form without the adverbial suffix. This word is more commonly encountered and shares the same meaning of intense or passionate behavior. Spanish students might also recognize the suffix '-mente' from many other Spanish adverbs like 'rápidamente' (rapidly), 'felizmente' (happily), or 'naturalmente' (naturally).

English speakers will readily recognize the cognate 'vehement' and 'vehemently', which come from the same Latin root 'vehemens'. These words maintain very similar meanings to their Spanish counterparts, describing intense, forceful, or passionate feelings or actions. The English word 'mental' is also distantly related, as it comes from the Latin 'mens' (mind), which forms part of the original compound word.