The Spanish word 'ruído' (meaning 'noise') traces back to the Latin word 'rugitus', meaning 'roar' or 'roaring', which itself comes from the Latin verb 'rugire' meaning 'to roar'. The word evolved through Old Spanish 'roido' before taking its modern Spanish form. This etymology shows how a word that originally referred specifically to the roaring sound of animals broadened its meaning over time to encompass any kind of noise or sound.

The Spanish word 'rugir' (meaning 'to roar', especially referring to lions or other animals) is a closely related word that comes from the same Latin root 'rugire'. While 'rugir' maintained the specific meaning of animal roaring, 'ruído' evolved to describe noise in general.

While not exactly the same root, English speakers might find it helpful to connect 'ruído' with English words like 'rude' and 'raucous', which share similar sounds and also have connections to noise or harshness. The English word 'roar' itself, while from Germanic rather than Latin origins, provides a good sound and meaning association with the Spanish 'ruído'.