Euphemism for
guts -
organs, the
lymphatic system - that sort of
stuff. The parts of an animal you wouldn't want to
eat unless they were called
sausages (if you are of the animal-
masticating persuasion, that is.)
Can also refer&to those things less tangible - thoughts and particularly emotions.
"My insides feel all gooshy."
Butterflies in the stomach? (literally!) Or mere anxiety?
They both fall in this domain.