Dixieland music is a style of jazz that began in New Orleans. It's a combination of blues, French music, trumpet, clarinet, piano, guitar, banjo, drums, and other similar instruments.
St. Charles Avenue is a street in New Orleans that is known for the wealthy homes that stand there, specifically in the Garden District. During Mardi Gras, parade routes are along St. Charles Avenue.
A poor boy, also known as po' boy, sandwich is similar to a sub sandwich. It is a typical food of Louisiana and is usually filled with meat.
Beau's last name, Andreas, is a common last name. Andreas is a name with Greek origins that generally means "man". It can be interpreted to mean "warrior".
Five finger grass is also known as silverweed. The five fingers in the name refer to the leaf's five segments. From Nina's perspective, the five finger grass will ward off evil and bring good luck to Ruby.