What is the origin of the idiom "like a knife through butter" and when to use it?

The idiom "like a knife through butter" does not have a specific documented origin, but it is a figurative expression that likens the ease of an action or task to the smooth and effortless way a sharp knife can cut through butter. It is used to describe how smoothly or easily something is done, as if there were no resistance or obstacles. It is a metaphorical expression that likens the ease of a task or action to the effortless way a sharp knife can cut through butter.