Bob, I meant "Liza," "L(o)u," and "Lulu" only as appearing in folksong and verse, not generally. (Though in decades of teaching I've never had a student with any of those names !)

"The lady that's known as Lou" is the femme fatale in Service's "Shooting of Dan McGrew," as mentioned. Also in the bawdy parody in circulation since at least the early '40s.