They were also called this prior to the Berlin Blockade/Berlin Airlift because C-47's and other transports ferried and dropped supplies to the troops. Another nickname for the cargo planes of the Berlin Airlift was the German term rosinenbomber (raisin bomber). Wikipedia link

Image credit: http://www.hoganwings.com

Other nicknames over time - Gooney Bird, Skytrooper, Tabby, Cab, Dumbo, Sister Gabby, Spooky, Puff the Magic Dragon, Dowager Dutchess, Old Methuselah, The Placid Plodder, Dizzy Three, Old Bucket Seats, Duck, Dak, Dakleton, Vomit Comet

And thank you Noisette , for this video by Michael Palin, showing a restored roseninbomber over Berlin.