As she shook her wooden leg

When given a present of some sort, the older members of my family would sometimes reply with the quaint phrase "Thankyou Sir, she said, as she shook her wooden leg". An old music hall expression?

I have seen other inquiries about this expression, but no one seems to give a better explanation than your proposal. There's a discussion of it on the Mucat Café Website. See:

www.mudcat.org

You have to scroll down a ways to see it, but the discussion is interesting.
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