Spittle

Spittle offers a feasible interpretation. It is something we maintain an internal dislike for and as a sign of belief.
When people have an arrangement, they spit on their own palms and shake hands to seal their word. However, we have seen people spit in defiance when being held down. Whenever we say “spit it out”, we are talking about getting someone to share a bit of information or uncomfortable fact. Perhaps you need to “spit out” something or get something free from your body in real life.