Get a move on, get started; its meaning is not a problem but its origin is debatable. For example, the OED dates the expression crack along, meaning to move briskly, from as long ago as 1541. Can we assume from this that people might have said or written since then, “let us get cracking along?” and may even have occasionally dropped the word ‘along’? However, because of the meticulous rules of first citations, etymologists Eric Partridge and others are forced to date get cracking from c. 1937, some four hundred years after people began to use the expression cracking along. The reader is left to draw his or her own conclusion. See also get weaving.