Green’s Dictionary of Slang

(US black) a generic name for a dance, esp. the current vogue step.

1977		in DARE.
1994		C. Major Juba to Jive 10: Applejack n. (1950s–1960s) tag name for dances, the latest dance step.
2000		Western Creations 🌐 Applejack Description: 40 count, 4 wall line dance. Alias: Tennessee Express.