The Spanish verb 'enseñar' (to teach) comes from the Latin word 'insignare', which meant 'to mark into' or 'to point out'. This Latin word was formed by combining two elements: the prefix 'in-' meaning 'in, into' and the verb 'signare' meaning 'to mark'. The verb 'signare' itself was derived from the Latin noun 'signum' meaning 'sign' or 'mark'.

The semantic evolution from 'to mark into' to 'to teach' makes intuitive sense - teaching is essentially the act of marking knowledge into someone's mind or pointing out information to them. This connection between marking/signing and teaching has persisted in Spanish educational contexts.

Several common Spanish words share this Latin root 'signum': 'seña' (sign, signal), 'señal' (signal, sign), and 'señalar' (to point out, to signal). You can see how all these words relate to the concept of marking or indicating something, just like 'enseñar' indicates or points out knowledge to students.

English speakers might recognize the connection to several familiar words that come from the same Latin root 'signum': 'sign', 'signal', 'signature', and 'designate'. Just as these English words involve marking or indicating something, 'enseñar' indicates knowledge to learners. The English word 'insignia' (a distinguishing mark or sign) is particularly close to the Latin 'insignare' from which 'enseñar' derives.