Jack, your reference to the Rock and Wee Pickle Tow set me searching. I have a dance of that name in a BBC pamphlet from a series of Barn Dances that they did 20 or so years ago.
Mudcat Lyrics gives me a Scottish Nursery Rhyme to the tune Rock... (that I sing an English version of to Lilli Bolero, to my granddaughter), Google tells me who wrote the poem.
But I can't find the words so I still don't know what the title means and I've often wondered.