The Spanish word 'rato' meaning 'a short period of time' comes from the Latin word 'raptus' meaning 'seized' or 'snatched', which itself derives from the Latin verb 'rapere' meaning 'to seize' or 'to snatch'. The semantic evolution from 'seizing' to 'a period of time' likely developed from the notion of 'snatching a moment' or 'seizing an instant', eventually coming to refer to that brief period itself.

Some related Spanish words include 'rapto' (kidnapping or abduction) and 'raptar' (to kidnap), which maintain a closer connection to the original Latin meaning of seizing or snatching.

English speakers might recognize the connection to words like 'rape' and 'raptor', both of which come from the same Latin root 'rapere'. A raptor is literally 'one who seizes' (think of how birds of prey seize their targets), while 'rape' developed from the violent sense of seizing or taking by force. The word 'rapid' is also related, originally referring to seizing or snatching quickly, which evolved to simply mean 'fast' or 'quick'.