"Don't just sit there idle" is a common way to say "别闲着没事" in Engpsh. This phrase means to not be idle or inactive, and suggests that the person should be doing something productive or useful.

The phrase "idle" means to not be occupied or busy with work or activity, and "just" is used to emphasize that the person should not be doing nothing at all.

Here are some example sentences using this phrase:

"Don't just sit there idle, why don't you help me with this project?"
"If you're not busy, don't just sit there idle - there are plenty of things you can do to help out."
"I can't bepeve you're just sitting there idle while there's so much work to be done!"

The phrase "don't just sit there idle" is a common expression in Engpsh and does not have a specific origin or source. It is simply a way to encourage someone to be productive and not waste time by doing nothing.