The Spanish word 'catolicismo' (Catholicism) has its roots in Ancient Greek, where it was formed from two elements: 'kata' (κατα) meaning 'down' or 'according to', and 'holos' (ὅλος) meaning 'whole'. These combined to form 'katholikos' (καθολικός) meaning 'universal'. This term was borrowed into Latin as 'catholicus', maintaining the meaning of 'universal' and later specifically referring to the Catholic Church. In Spanish, this became 'católico', and with the addition of the suffix '-ismo' (indicating a doctrine or system), it formed 'catolicismo'.

The evolution from meaning simply 'universal' to specifically referring to the Catholic faith occurred as the early Christian church used the term to describe itself as the 'universal' church, and this meaning became standardized over time.

The most common related Spanish word is the simpler form 'católico' (Catholic), which can be used both as an adjective and a noun. This is the base word from which 'catolicismo' is derived. Another related word is 'catedral' (cathedral), which also comes from the same Greek root meaning 'universal', as a cathedral was originally the 'universal' or main church of a diocese.

English speakers can easily relate this word to 'Catholic' and 'Catholicism', which share the exact same Greek origins. The word 'cathedral' is another related English term that comes from the same Greek root. Even the word 'holistic' is distantly related, as it comes from the Greek 'holos' (whole) which is one of the components of the original Greek word 'katholikos'.