ETYMOLOGY
??? – perhaps from the Scottish ‘rattlebag‘ (a bag filled with small stones and hung on the end of a stick to make a rattling noise)
EXAMPLE
“…In the North of England children call, or used to call, thunder Rattley-bags, and to sing this couplet during a storm –
Rowley, Rowley, Rattley-bags,
Take the lasses and leave the lads…”
From: Notes on the Folk-Lore of the Northern Counties of England and the Borders
By William Henderson, 1879
Lexicophilia 