The Spanish verb 'registrar' (to register) comes from the Latin word 'regestum' meaning 'register', which itself was formed by combining two Latin elements: the prefix 're-' meaning 'back' or 'again', and 'gestum' meaning 'to carry' or 'to accomplish'. The Spanish word was created by adding the common verb suffix '-ar' to 'registro', the noun form meaning 'register'.

The evolution of meaning is quite logical - the original Latin components suggest the idea of 'carrying back' or 'recording again', which evolved into the modern concept of registering or recording information in an official capacity.

A simpler and very common related Spanish word is 'registro' (register, record), which is the noun form from which 'registrar' was derived. You might also encounter 'registrador' (registrar, recorder) and 'registrado' (registered), which are all part of the same word family.

English speakers will find this word easy to remember as it's closely related to several English words including 'register', 'registration', and 'registry'. All these words share the same Latin root 'regestum'. Even the English word 'registrar' (an official who keeps records) comes from this same source, though it functions as a noun rather than a verb like its Spanish cousin.