A milkshake is the shaking of milk. Cultures like using it because it makes them high but they can also concoct (who knows what the word means) the disease Flippinitous, which can be very deadly, aside from other deadly viruses such as Swine flu, cancer, and Michael Jacksonitous, all very deadly indeed.
Milkshakes have been around for quite a long time now, due to their very sexual reproduction levels (on a scale of 1 to 10, its a 45) because that's all they do, other than sit there and do nothing.
The first milkshake was located across the Rocky Mountains in Canada, where they discovered a large Hyena next to it, drinking it, which would make it reproduce. So, it reproduced to three milkshakes, then five, then seven, then nine, the one million, and then the earth was dominated by milkshakes.