I have come across it in Crash Course World History. It is at 7 minute and 37 second. Here it goes:
Without adequate water supplies for irrigation, the cities could not sustain themselves, so people literally just picked up and left for greener pastures.
It seems to me that pick up means to pack one's belongings there, but I am confused because the Machmillan and Longman dictionaries do not give this definition. Is that some non-standard use of pick up?