On Conan O’Brien’s late-night show “Conan,” actress Kathy Bates revealed just how she nailed the Baltimore — excuse me, Bawlmer — accent in her role on “American Horror Story: Freak Show” a couple of years ago.

Bates’ character, Ethel Darling, sported a twangy dialect with heavily rounded “O’s” that sparked much debate among linguists and confused watchers (though Baltimoreans understood right away).

On Wednesday night’s “Conan,” Bates told O’Brien she practiced the accent’s distinctive phonetics by singing the national anthem.

Then, she recruited O’Brien to sing with her. Both seemed to give their best attempt, though they conspicuously missed the hearty “Oooh!” before the song’s final couplets.

Francis Scott Key would be so proud.

—?Danielle Ohl