Merp can be used in an catch-phrase to throw people off guard or to have one beg the question Does this person really think he is a grammatitician, I think not! Additionally, one can use the word merp as a euphemism in public as not to offend any people in proximity.
Natural birth to some women means a labour without any medical pain relief, leading to a vaginal birth, and possibly third stage, without any interventions at all. Midwives and obstetricians have their own working definition of natural birth, which sits somewhere in between these different viewpoints.
Born of water refers to the first birth, since in the womb babies grow in a bag of fluid very similar in composition to sea water. Just prior to birth, the bag breaks, releasing this water and commencing the birth process. Born of the Spirit is the second birth, what we call being born again.