Short answers, pulled from the story.
The English word baptism traces its lineage back to the neuter Greek noun baptisma, which emerged as a neologism within the New Testament. This specific vocabulary did not exist in pre-Christian Jewish texts or the Septuagint, marking a distinct linguistic shift in religious history.
Baptismal practices emerged from Jewish ritualistic traditions during the Second Temple Period where figures like John the Baptist utilized water rites as central sacraments. Texts from Qumran known as the Dead Sea Scrolls describe rituals involving sprinkling bathing and immersing to achieve spiritual cleansing.
Traditionally a person is sprinkled poured or immersed three times for each person of the Holy Trinity in what is called trine baptism. Immersion refers to any form of dipping whether the body is put completely under water or only partially dipped while submersion describes the form where water completely covers the candidate's body.
Pope Pius XII wrote in his encyclical Mystici corporis Christi of the 29th of June 1943 about baptism making members of the body of Jesus Christ. The Catholic Church teaches that baptism configures the person to Christ and obliges them to share in the church's apostolic activity.
Until the Middle Ages most baptisms were performed with candidates naked as evidenced by early portrayals and writings from Church Fathers like Cyril of Jerusalem. Deaconesses helped female candidates maintain modesty during these ceremonies while men remained exposed before changing customs regarding modesty contributed to the practice of requiring baptismal robes which are almost universally white today symbolizing purity.