The Spanish verb 'jurar' (to swear) comes from the Latin verb 'iurare', meaning 'to swear or take an oath'. The Latin 'iurare' itself was derived from 'ius', meaning 'law' or 'justice'. This etymology reflects how the act of swearing or taking an oath was closely tied to legal and judicial matters in Roman society. The evolution from Latin 'iurare' to Spanish 'jurar' shows a typical sound change where the Latin 'i' became the Spanish 'j' (pronounced like an 'h' in modern Spanish).

Several common Spanish words share this legal root, including 'jurídico' (legal), 'jurado' (jury), and 'juez' (judge). All these words maintain a connection to the original Latin concept of 'ius' (law and justice). The word 'perjurar' (to perjure) is also related, specifically referring to false swearing or breaking an oath.

English speakers might recognize this etymology in words like 'jury', 'jurisdiction', and 'judicial', all of which come from the same Latin root 'ius'. The English word 'perjury' is particularly close to Spanish 'perjurar', both referring to false swearing and both derived from Latin 'periurare'. The connection between all these words helps illustrate how concepts of law, justice, and oath-taking are deeply interconnected in both languages.