Hi, I'll try to get back to you soon, but to give you a short answer, it is a Christian version of Circumcison as both serves to set apart them from the world.
The obvious difference is that Baptism is a rite that doesn't involve a surgical proceedure. It evolved from the Hebrew rite of purification, via, water. A preview to the kind of Baptism that is practiced today by Christians was when Elisha instructed Namaan the Syrian to dip himself in water seven times so that he will be healed of Leprosy.
In the New Testament the practice was carried on by John the Baptist for purification "I baptize you with water for purification but he will baptize you with fire". Eventually, Baptism became an illustrative rite of passage.
When the person is submerged and re-emerged from the water, s/he is not only illustrating the death, burial, and resurrection of Christ but also demonstrated what has happened to him/her spiritually. "An outward sign of an inward change". We call that change Born Again, when one is transformed from a God-hating soul (Genesis 8:21 & Psalm 14) to one who loves God and obey His commandments. Ezekiel spoke of this change in ch 36:
24 For I will take you from among the heathen, and gather you out of all countries, and will bring you into your own land.
25 Then will I sprinkle clean water upon you, and ye shall be clean: from all your filthiness, and from all your idols, will I cleanse you.
26 A new heart also will I give you, and a new spirit will I put within you: and I will take away the stony heart out of your flesh, and I will give you an heart of flesh.
27 And I will put my spirit within you, and cause you to walk in my statutes, and ye shall keep my judgments, and do them.
28 And ye shall dwell in the land that I gave to your fathers; and ye shall be my people, and I will be your God.
Back to Baptism Paul, the writer of the book of Romans that is in the New Testament said that they participated in the death, burial, & resurrection of Christ (Romans 6:3-4). The Baptismal rite is done publically as so to identify him/herself as a Christian