“I’m Just Popping Out” Means “I’m Leaving Briefly”

In an Australian office or home, “I’m just popping out” usually means “I’m leaving briefly and will be back soon”, not “I’m suddenly jumping out”. Pop out makes the trip sound short and casual. It commonly appears with for coffee, to the shops or for ten minutes.

A: Where are you going? B: I’m just popping out for coffee. I’ll be back in ten.

Go out simply means leaving and can also refer to an evening social activity. Pop out puts more emphasis on a brief absence. This use is also common in British English. In a formal setting, or when timing matters, “I’ll be away for ten minutes” is clearer.

https://dictionary.cambridge.org/dictionary/english/pop
https://www.abc.net.au/listen/programs/canberra-breakfast/cafe-owner-caleb-evans-billy-ts-teddy-picker-shadow-pandemic/13737470