The word baptism comes from a Greek word, which means 'to bathe, dip or plunge in water'. The English evangelist, Trevor Dearing, in a light-hearted moment, once likened baptism to the action of becoming a holy tea-bag'! - Plunged into the water to enable 'all the flavour to come flooding through!'
Seriously, baptism is laden with a wealth of symbolic meaning and significance. Water, which sustains life, can also kill. Being submerged in it, even for a religious purpose, can convey the impression of undergoing a form of 'death'. 'Dying' and 'rising' as well as being ritually cleansed and purified; these images have all been used by the Church, as they have by many religious traditions, to mark the stage of admission, or initiation through total repentance and conversion. In the Gospels we see Jesus being baptised by John the Baptist.
Many years later the Gospel writers linked this event with what happened to the apostles at Pentecost, when the Holy Spirit was 'poured out' on them. The early Church thus introduced baptism in the name of Jesus as the way of receiving his Spirit, and thereby joining the community which met in his name for teaching and the breaking of bread. So initiation into the Church was made up of the following: water baptism - outpouring of the Spirit - Eucharist. This is still the pattern today. The three Sacraments of Baptism, Confirmation and Eucharist make up the Sacraments of Initiation into the Church.
According to the Acts of the Apostles large numbers of people were baptised with no preparation beyond a 'profession of faith', the declaration of their belief in Jesus as the Christ. As the Church began to meet hostility and persecution there emerged a structure for preparing people for initiation into the Church. In order to test the seriousness of a person's interest in the Church, and also to weed out the possible entry of spies into the community, as well as eliminating as far as possible the scandal of apostasy (the public denial of Christ by a Christian), the Church began acatechumenate. This provided a lengthy period of preparation for prospective members, and celebrated their gradual acceptance into the community by means of certain rituals, until the solemn moment during the Easter celebration when they received the Sacraments of Baptism, Confirmation and Eucharist together, and so became fully initiated members. There was also a long period of after-care for the continuing involvement of the newcomer into the life of the community.