Not strictly folk, but I can always remember which is which, Medicare (for the elderly) and Medicaid (for the poor), because of Allan Sherman's parody of "Saint James Infirmary."

I went down to Mount Sinai Hospital
To see my old zeyde there (zeyde is Yiddish for grandpa)
And I said, thank God for the Blue Cross
And I wish we had the Medicare.

   It just came up today as I was grading papers and I instantly recognized that one of my students had gotten Medicare and Medicaid wrong.