In his glossary, Professor Child defines 'rock' or 'roke' as 'distaff'. The first 2 meanings for 'distaff' in the Macquarie are: 1. a staff with a cleft end, formerly used for holding the wool, flax etc from which the thread was drawn in spinning by hand; 2. an analagous part of a spinning wheel for holding flax to be spun. The second conforms with what Kim posted above.

In versions of 'Baron of Brackley', Brackley's wife wants to arm the women with 'rocks' to shame Brackley into action:

She called on her marys, they came to her hand
Cries, bring me your rocks, lassies, we will them command

She called on her women and bade them in
'Tack a' yer rocks, lasses, we will them comman

But lasses tak down your rocks and we will defend

--Stewie.