The Spanish verb 'castigar' (to punish) comes from the Latin verb 'castigare', which meant 'to correct' or 'to punish'. The Latin word itself is a compound formed from two parts: 'castus' meaning 'pure' or 'correct', and 'agere' meaning 'to do' or 'to drive'. So etymologically, 'castigar' literally meant something like 'to make pure/correct' or 'to drive toward correctness', which evolved into the modern meaning of punishment or correction.

A related Spanish word is 'casto' (chaste, pure), which comes directly from the Latin 'castus'. While 'castigar' developed to focus on correction through punishment, 'casto' retained the original meaning of purity, particularly in a moral or sexual sense.

English speakers might recognize the connection to words like 'castigate' (to criticize or punish severely) and 'chaste' (pure, virtuous), both of which share the same Latin roots. 'Castigate' is particularly close to 'castigar' both in form and meaning, as both descended from Latin 'castigare'. The word 'chaste' comes from Latin 'castus', showing how the notion of purity or correctness has been preserved in English as well.