Where does prednisone come from? Is it naturally occuring so that some some herbal medicines could contain prednisone?

Man made. Prednisone is a man made drug to mimic the effects of steroids our body produce from from the adrenal glands. Prednisone is not a naturally occurring medication. Some supplements can be contaminated with substances that can mimic steroids so you need to be careful.
Synthetic. Prednisone is synthetic. Many of the so called herbal or natural medicines are some times adulterated with conventional drugs.