My Iowa-born (1912) mother always used the phrase following anytime she or anyone in her presence cried "Aha." Mom would always follow it with "she cried and waved her wooden leg aloft."

Today I was in another room and heard my wife say "Aha" as she was watching TV. So I said "...she cried and waved her wooden leg aloft."
Then I wondered what that meant, if anything, and where in the world it came from.