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.
Language learning is natural. Babies are born with the ability to learn it and that learning begins at birth. All children, no matter what language their parents speak, learn a language much the same way. This learning takes place in three basic stages.