What cause butterflies surrounded by your tummy when you are twitchy. Why does it develop?

What cause butterflies surrounded by your tummy when you are twitchy. Why does it develop?
When you're nervous or afraid, the body produces chemicals, one of which is adrenaline. The presence of this cause your solar plexus to tighten, (that's in your abdomen) and cause nausea, stomach pain etc. In severe cases vomiting is also a symptom.
=D "Butterflies" seem like a much less-scarier word, don't you ruminate?
Stress or nerves usually causes some physical criticism such as an increase in blood pressure, perspiration, butterflies surrounded by your tummy, shakiness, forgetfulness, clumsiness, clouded judgements, impaired brain function, disorientation and numerous others.