The Spanish word 'bronco', meaning 'rough' or 'harsh', has its roots in ancient Greek and Latin. It comes from the Latin word 'bruncus' meaning 'throat' or 'hoarse sound', which itself derived from the Ancient Greek 'bronchos' (βρόγχος) meaning 'windpipe' or 'throat'. The meaning evolved from referring to the throat and hoarse sounds to describing things that are rough or harsh in general, likely due to the association with rough, hoarse voices and sounds coming from the throat.

This word is related to other Spanish words like 'bronquitis' (bronchitis) and 'bronquios' (bronchi), which maintain a more direct connection to the original anatomical meaning referring to the airways and throat.

English speakers might recognize this word's connection to medical terms like 'bronchus', 'bronchial', and 'bronchitis', all referring to the airways in the throat and lungs. The English word 'bronco' as in the wild or untamed horse was actually borrowed directly from Spanish 'bronco', referring to the rough, harsh nature of an unbroken horse.