What is the difference between "Knock it off!" and "Drop it!". I do translate both as "Stop it". Is there any context-based usage difference? Thank you.
Drop it will usually refer to a conversation or argument that is repeatedly going over a point that has been addressed (but not to the satisfaction of one party). It replaces the statement "I know that you are dissatisfied with the response, but it is the only one you are going to get. So please cease this line of argument."
Knock it off has a broader application to any (often repeated) annoying behaviour. So if the person told to "Drop it!" decided to show their continuing displeasure by noisily opening and closing drawers or tapping a pen on his coffee mug, then you might tell him "Such juvenile displays of petulance will not make me change my mind. Please desist." or Knock it off!
Knock it off: Stop what you are doing - stop irritating me with your words/behaviour
Drop it: Never mind, forget about it, stop this conversation before it escalates
They could be used interchangeably in a heated discussion, but to me the first one is more agressive and behaviour oriented than the second which is to my mind only conversation related