I think 짠짜라 comes from this word, 짠하다? Watch the following music animation and see what you think:
Here is another version of 짠짜라. I think this one was filmed in Incheon in a park near the bus terminal.
Update: Here is the music video for 짠짜라.
Here is another video with questionable linguistic value: Bin 2 A.M.