The Spanish verb 'agendar' (to schedule) comes from the Spanish noun 'agenda' combined with the common Spanish verb suffix '-ar'. The Spanish 'agenda' itself comes from the Latin word 'agenda', meaning 'things to be done', which was derived from the Latin verb 'agere' meaning 'to do' or 'to act'. This evolution shows how the concept of 'things that need to be done' developed into the more specific meaning of scheduling or planning activities.

A simpler and more common Spanish word related to 'agendar' is 'agenda', which means a schedule or planner. While 'agenda' is the noun referring to the physical or digital planner itself, 'agendar' is the verb form meaning the act of scheduling or putting something on the agenda.

English speakers will recognize the cognate word 'agenda', which has the same meaning as in Spanish - a list of things to be done or a schedule of activities. Both the English and Spanish words preserve the core meaning from Latin of 'things that need to be done'. The English word 'agent' is also related, coming from the same Latin root 'agere' (to act), referring to someone who acts on behalf of another.