The Spanish word 'rápido' meaning 'fast, quick' comes from the Latin word 'rapidus', which meant 'quick, snatching'. The Latin 'rapidus' was formed by combining the verb 'rapere' ('to seize, snatch') with the suffix '-idus', which was used to form adjectives describing qualities. The evolution from the idea of 'snatching' to 'quick' makes intuitive sense, as something that snatches or seizes tends to move quickly and suddenly.

Several common Spanish words share this Latin root 'rapere', including 'rapto' (kidnapping), 'rapaz' (predatory), and 'rapiña' (plundering). All these words maintain a connection to the original meaning of seizing or taking something quickly and forcefully.

English speakers might recognize this etymology in words like 'rapid', 'raptor' (a predatory bird that seizes its prey), and 'rapacious' (aggressively greedy). The word 'rape' also comes from this Latin root, originally meaning 'to seize or take by force'. The English word 'rapid' is a direct cognate of Spanish 'rápido', both preserving the sense of quickness from Latin 'rapidus'.