'combatir' originates from Latin (via Vulgar Latin), specifically the word 'combattere', where 'com-' meant 'together' and 'battuere' meant 'to beat/strike'.

'combatir' changed from Vulgar Latin 'combattere' (and Old French/Occitan forms) into Old Spanish forms like 'combatre'/'combatir' and eventually became the modern Spanish 'combatir'.

Initially it meant 'to beat or strike together' (i.e., to engage in striking), and over time it evolved into the broader sense of 'to fight, to oppose, or to counteract'.