What is the origin of the idiom "holy shit" and when to use it?

The idiom "holy shit" is used to express extreme surprise, shock, disbelief, or intense emotion. It is a stronger and more explicit version of expressions like "holy cow" or "holy moly." This expression should be used with caution. It is not suitable for formal or polite conversations, and its usage depends on the context and the people you are interacting with.