Variant of the name of a traditional tune of Celtic and greater Britain..."regarding the title, a rock is a distaff, a device that holds the flax strick or the fiber for spinning. It is called a rock because the weight, or whorl, was frequently a shaped and pierced rock. A 'wee pickle tow' is a small piece of prepared short flax fibers combed from longer fibers called "line". Thus it was a spinning song..." Source.
The tune appears in the 1663 edition of Playford’s Musicks Hand-Maid under the title "A Scotish March."