The last thing the police want someone they’ve arrested to do is think too hard. They want someone who is suspected of a crime to get scared and confess all they’ve done. So they say things like, “Spit it out! We know you did it! Just confess and it will be much better for you.

To spit something out means to say it without thinking about it all that much. Think about what it’s like to have something stuck in your throat. You just want to get it out as quickly as possible, so you spit it out as fast as you can.

Well, the same applies to words. Michael Stipe is famous for lyrics of great songs like “Losing My Religion,” but since songwriting isn’t easy, it’s still a challenge for him. He says he does his best work under pressure, when he has to be done quickly. He doesn’t think too hard about the lyrics. He just spits them out.

When you want someone to give up a secret, you can also say, cough it up. It means the same thing as spit it out in that context. You wouldn’t cough up lyrics though. That wouldn’t sound very good.