Baptism is a Christian religious rite of sprinkling water on to a person’s forehead or of immersing them in water, symbolizing purification or regeneration and admission to the Christian Church.
 

The origin of baptism:

The act it’s self originates from the religion of Abraham known as Judaism.

In Judaism the Hebrew name for the ritual of baptism is known as Mikvah.
In Matthew 3:13-17 the Gospels report that Jesus was baptized—a historical event from whence the ritual of baptism which is done by the Christian originates it’s roots from. 

The meaning of baptism:

The word baptism means to purify by water, to sett a part for a holy purpose, to initiate, to ordain, to inaugurate or to mandate someone, so that he may go forth and carry out a special mission.

John the baptist baptises Yeshua (Jesus):

When John the baptist, Baptised Yeshua whom the Christians call Jesus, the act of baptism was done as symbolic ritual known as Mikvah, which was practised in Abraham’s religion known as “Judaism“. 

The baptism of Jesus was done to spiritually mandate, to inaugurate and launch Him into his own ministry. 

Spiritual meaning and purpose of baptism:

Baptism is a visible act with a spiritual meaning.

It symbolises Christ burial and resurrection, one’s entrance into the water identifies the person with Christ’s death on the cross, his burial in the tomb, His resurrection from the dead, and His present state where He sits on the right hand side of His father in Heaven.

Baptism has been called a holy sacrament and an ordinance of Jesus Christ.

In many denominations, baptism is performed on young children and is accompanied by name-giving.“the sacrament of baptism”

synonyms:

christening, naming, immersion, sprinkling; rarelustration “the baptism ceremony” a ceremony or occasion at which baptism takes place.

plural noun:

baptisms “weddings, funerals, and baptisms are carried out in the parish church”
A person’s initiation into a particular activity or role, typically one perceived as difficult. “this event constituted his baptism as a politician”