...and says she's paid off their mortage by saving her "butter & egg money"; what is "butter & egg money"?
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the Clampetts are in a fancy Beverly Hills jewelry store. Granny points to a tray of rubies.
Granny: "How much fer one o' them red diamonds?"
clerk: "Madam, those are rubies."
Granny: "OK ask her kin we buy one offa her."
clerk: " The ruby I am talking about is not a lady."
Granny: "Lissen, how she got them diamonds is her business. I'm just sayin' ask her kin we buy one from her."
I think she's using it as a euphemism for money she earned herself.
Traditionally, a farm wife would usually tend to feeding chickens and milking the cow. Any eggs and milk she gathered in excess of what the family needed could be sold for cash.